I have flatness at mid face. Is it a massater or maxilar problem. Why? (Photo)

Flatness in the mid face can be helped with Juvederm Voluma XC injections.  This would be on-label treatments.  You could also do off-label injections with Voluma to your jawline and chin to help with symmetry and enhance masculinization.  With fillers it is important to be conservative to maintain a natural appearance. Good Luck.   

you are a good looking guy, and if you want to look more masculine filler placed in the right locations (mid cheek, jawline, mandible) would do very well to give you a subtle masculinization.  otherwise, you look normal for your age.  I would not suggest mandibuilar botox as that can round your face which would not look attractive on you.  I would suggesting increasing the size of your masseter area by using fillers.  If you are considering anything, go to someone very well trained in treating men.  Best, Dr. Emer.

....thats all you need. I agree with the Plastics experts who already answered the question. I would do only a tiny bit of filler, 0.5 ml maximum to the mid cheek area. Fillers in males are different to fillers in females. Jawline / Mandible fillers can also accentuate the masculine jawline, especially at the angle, below your ear. I would use Juvaderma Voluma here as well. Subtle, but natural looking is what you want. RegardsDr Davin Lim Laser and Cosmetic DermatologistBrisbane, Australia. 

I believe you would benefit simply from some fillers to give your face more angularity.  Angularity is a very  masculine trait (Brad Pitt)!  Adding the appropriate filler to the appropriate area gives a great result!  See the link below for an easy 10 minute treatment.