To elongate the life of a weft-cutting device in a loom.

A control computer C1 computes the rotation speed of a loom on the basis of rotation angle information obtained from a rotary encoder 27. The control computer C1 divides the output time of an overexcitation time on the basis of the computed loom rotation speed and a data table exhibiting the corresponding relation of memorized rotation speed-overexcitation time, and the overexcitation signal is outputted into a driving circuit 22 only for the output time. The driving circuit 22 applies the overexcitation voltage to a rotary solenoid 12 only for the output time. A movable blade 23 attached to the output shaft 121 of the rotary solenoid 12 is moved in the direction for cutting a weft Y. 24 is a fixed blade.