How to cope with that coworker?

We are at the same age, and we were close friends, he always wants to show me that he is better than me, he buys anything similar to what I buy, he always wants to show me that he is more popular, and that he is more clever and better than me in the work.

I am always kind to him (my nature) even supported him in some critical situations he passed by, but he treats most people in extremely nice way but treats me in cold way, he wants me to feel lonely in the work place.

For some reasons this coworker got promoted and I am not, he always makes a show that he is higher than me in the hierarchy.

There are a lot of details but this is a summary.

Maybe he recognizes that you are clever, popular, and good at work, so he tries to show that he is too (shows himself, shows others, and maybe shows you too?).
And maybe when he's very nice to others yet cold to you - it's his social way - like he's in control - possibly not really genuinely so nice to them - it's for show. He's showing them how nice he is - is he being manipulative? Is he feeling threatened by them? There is someone who works where I do - and there's this sense of one-up most of the time (anything that I say - this other person will say something to "top" it, and this person seems so nice and understanding with others yet becomes nasty with me in private (others don't see this). I've concluded that this person maybe has a low self-esteem from early on, perhaps it's more noticeable when around someone else who has demonstrated success, and perhaps there are some reasons for this kind of social behaviour.

Rose, many thanks for your very good reply, you really understood the situation. He is jealous of me at work and also some of personal aspects, he has some kind of inferiority complex, he feels provocative when hears someone talks good about me also, he has lots of insecurities.

Indeed, he is SO MANIPULATIVE.

Other people don't really realize he true manipulative disrespectful personality.

I don't know how to handle him, we are in one office and I feel miserable being with him along the day.

Seawhale......I feel your pain. I live next door to a MAJOR manipulator who has managed to fool everyone except me. This person competes with me and I can never trust anything that comes out of her mouth because there is always a hidden agenda. I'm forced to see this person all the time and pretend to like this person for the sake of getting along as neighbors, but I have to tell you.....it's pure hell. I've never been good at being nice to people I don't like. The way I see it, it's my life and if you don't add anything positive to it, then I have no use for you. Sounds like you're in a similar situation.

How to cope with him? Ignore him. I know that his a simple reply, but I once dealt with a coworker who was manipulative and tried to get under my skin (successfully) for 7 years. It was hell. If I had just ignored him and had kept my eyes on my own paper, so to speak, I would have avoided a lot of mental anguish. It's really hard, but it's probably the best solution. (And sometimes people are just looking for a reaction...don't give it to them. They'll eventually stop.)

You said you "were friends". What happened? Did this happen before he became mean or after?