The method of constructing of rotation curve for our galactic disk is developed .
Simple physical model shows that the velocity of the Sun around the center of the Galaxy must be less than currently accepted IAU value 220 km/s .
Independently obtained result for neutral hydrogen ( \lambda = 21.1 cm ) confirms the previous statement .
The values of the Sun ’ s velocity is about 110 km/s .
As a consequence , the rotation curve for the disk of our Galaxy is not flat , but it is a decreasing function of the distance from the center of the Galaxy .
This conclusion seems to be consistent also with other galaxies .