To provide a waist size-adjustable bottom garment so designed that the length of the waist part is adjustable and also the beauty of outward appearance is not spoiled.

This trouser body is structured as follows: the trouser body comprises a front side member (outside member) and back side member (inside member) which are partially overlapped each other to form pocket parts; wherein an inside second waist belt member 64a is positioned at the inside of a first waist belt member 50a, the front side member and the first waist belt member 50a are joined to each other, the back side member and the inside second waist belt member 64a are joined to each other, a position adjuster 80 has a rail member 82 fixed on the inside second waist belt member 64a and a slider member 92 fixed on the first waist belt member 50a, the rail member 82 is shielded by the first waist belt member 50a, a first belt rubber material 70a applies a force to the back end side of the first waist belt member 50a in a rearward direction, and the outside second waist belt member 62a shields the first belt rubber material 70a.