The invention discloses an electric clipper with a comb row and a movable blade adjusted by a knob. The electric clipper comprises a main frame, a comb row and a movable blade assembly, wherein a knob assembly is arranged in the main frame, is respectively connected to the comb row and the movable blade assembly, and comprises a box cover, a knob, a telescopic self-locking block, a rotary block, a box body, a spring, a bevel wheel, a fixing plug, a thread wheel and a pushing frame; the box body is fixed in the main frame; the fixing plug is arranged in the main frame at the lower end of the box body; the fixing plug and the bevel wheel are sleeved in a matched manner; the spring is sleeved with the middle part of the bevel wheel; the rotary block is buckled with the bevel wheel; the telescopic self-locking block is sleeved with the rotary block in a matched manner; the knob is sleeved with the rotary block; the box cover is sleeved with the knob, and is buckled with the box body; a sleeve is arranged at the side end of the box body, and is buckled with the thread wheel; a gear on the thread wheel is meshed with that on the bevel wheel; the thread wheel is in threaded connection with the pushing frame; and the telescopic self-locking block is sleeved with the upper end of the spring. The electric clipper provided by the invention is simple in structure and convenient in use, and can realize an ideal using effect by using the knob to control length of the comb row and the movable blade.