PURPOSE: To end operation simultaneously with the end of milling by serially connecting a mill motor, motor current detector and switching element and by comparing a detected value with a set current threshold.

CONSTITUTION: When the load current of a motor is lower than a first current threshold I1 at tone point of time T1 after 1-3 seconds from a start, coffee powder can be judged to be put in a mill and the extraction of coffee is started at once. On the other hand, when a motor current is higher than I1 and coffee bean is judged to be put in the mill, the current is compared with a second current threshold I2 at T2 after 5 seconds from T1; and when the motor current is higher than I2, the mill motor is judged to be in a locked state so that the motor is stopped and alarm is generated. When the motor current is lower than I2, coffee bean is judged to be put in the mill and the mill motor continues rotation so that milling of coffee bean proceeds. When the motor current is lower than a third. current threshold I3 at the point of time T3 after the lapse of a predetermined period of time from the point of time T2, milling of coffee bean is judged to end so that time rotation of the motor is stopped.