To normally keep the number of rotation of a drum to be a suitable rotation number by which the fall amount of internal cloth becomes the maximum amount.

A motor 14 for rotating the drum is driven by a vector control system by a control microcomputer 54 through an inverter circuit 45. A current detecting means 55 detects the effective value of a q-axial current in vector control. The control microcomputer 54 determines that an area with the maximum change width in the effective value of the q-axial current is the area where the maximum load torque change of the motor 14 is obtained. The number of the rotation of the drum in the stationary state of a washing operation is controlled to be the number of the rotation in the area where the determined maximum load torque change of the motor 14 becomes maximum.

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