A device for controlling a drying period of time in a washing machine which can control drying of laundry with an optimum period of time, comprises a non-conductive pipe arranged to drain water extracted from laundry well, a transmission voltage generating part, mounted inside of the non-conductive pipe, for generating a transmission voltage corresponding to the quantity of the draining water, a comparing part for comparing the transmission voltage with a predetermined reference voltage to generate a compared signal, and a microcomputer for controlling a motor for drying operation in response to the compared signal.