Why do my friend get aroused when he sees me?

Men and women's brains are wired differently, men are stimulated by what they see, images, photographs and this why men tend to use porn more than women.

A females body, it's very shape can be sexually stimulating for a man even when your not intentionally doing anything, wearing anything different, etc.
This can happen to men in a huge variety of situations with women they don't know, and even with women they don't even like so it's nothing personal.

The whole intention of Muslim women dressing covered from head to toe in black is intended to stop this very thing happening, but my experiences after spending time in Dubai where this is extremely common dress showed me it makes no difference.

I'm not saying that all men walk around constantly on heat (although some do) but you first of all must see this as just something we do rather than it involving you directly, he more than likely feels this with many women he meets.

It could be this guy does find you sexually attractive, he probably does and but then a huge number of men on this planet will also think about you this way.
I just wonder how you know he's aroused, if he's blatantly parading to you a huge bulge in his trousers then it's time to have a word about his behaviour.

Finally, weather he fancies you or sees you as a prospective girlfriend/ wife/ fling is a completely different question and not at all linked to if he finds you sexually attractive.

And now we're right back to how our brains are wired differently.

his arousal is a sign of interest in you. he probably doesn't realize he is doing this and generally if a guy faces his pelvis towards you he is subconciously interested. you should talk further with him and maybe ask him out to see if he is interested. I think his arousal is no big deal and he might be worth at least going to a movie or dinner with

He likes you. If you were both teens I'd say he was just horny & blunt, but you're not.

yep, supercheerchick has it right.
he likes you. ALOT.

umm I think he may have more of a sexual diseire with you

he likes you