Pants capable of adjusting the size of the waist are provided to adjust the size with one hand by installing a knob unit at the outer side and preventing inner and outer overlapped parts from being separated. The pants capable of adjusting the size of the waist comprise waist hem inner and outer overlapped parts(1,5) made of fabrics and overlapped on the waist belt of the pants formed above pockets; a guide rail(2) horizontally installed at the outer side of the waist hem inner overlapped part; a hook installed on the inside of the waist hem outer overlapped part; and a protection cloth(4) made of the same fabrics as the fabrics forming the waist hem inner and outer overlapped parts to prevent the guide rail from being exposed by covering the guide rail. The hook comprises a guide unit(31) formed in the middle of a body(32) to move along the guide rail; hinge units(33) arranged on both sides of the guide unit; a knob unit(34) rotatively combined with the hinge units; and hanging units(35) arranged on the guide rail at regular intervals, locked to the hanging unit, and formed at one end of the knob unit.
