First of all you need to understand that if a girl laughs at your cock, it will be for a reason. I can think of several possibilities:
A) She's a sadistic psycho-bitch.
B) She's retaliating against something negative you've said about her body.
C) You have given her the impression that you like SPH (small penis humiliation).
D) (insert idea of your own) ...
But to answer your question directly: You have not told us the measurements of your penis so all we have to go on is how big it looks in comparison to your hand and body, but it looks to be very much in proportion with you so, even if you are a very petite guy, I'd say that it looks good on you. But if you are average hight/build it looks like you have an average (or above average) penis. If you are a big guy, I'd guess that your penis is well above average size. So, either way your penis is not small and there is absolutely no good reason why a girl should laugh. On the contrary, I expect that girls will be very pleased to find what you're packing.