To readily set the operation speed of a weaving machine by taking a load in an opening driving motor into consideration.

A torque detecting circuit 35 constituting an operation speed control device C2 calculates a torque from a current value supplied from a driving circuit 30 to an opening driving motor 27. The value of the detected torque discovered by a torque detecting circuit 35 is compared with that of a standard torque memorized in a standard torque memory circuit 34 by a reference circuit 36. An operation speed is selected based on the compared result in the comparative circuit 36 by an operation speed selecting circuit 37. The operation speed selected by the operation speed selecting circuit 37 is inputted to a weaving machine controlling computer C1 to drive the Weaving machine at the operation speed inputted to the weaving machine controlling computer C1.