To provide a method and a device for start control of a single phase motor pump precisely functioning without receiving influence of external variation factor and not requiring installation of a centrifugal switch.

A motor terminal voltage detection circuit 5 and a capacitor terminal voltage detection circuit 6 of the single phase induction motor 1 are connected to a control box 7, and an auxiliary circuit switch 8 opened and closed by electric output signal of the control box 7 is attached to a motor auxiliary circuit. A constant specific to a motor calculated from ratio to motor terminal voltage under a no-load operation condition is determined, motor terminal voltage and capacitor terminal voltage at start are detected, the same are compared with the constant specific to the motor, and the motor auxiliary circuit is shut off with judging that switching speed conditions are met because an optionally predetermined condition value is reached.