A semiconductor device controller includes a current supply control unit for controlling a conduction state of a semiconductor device connected to a load in response to a control signal to supply current to the load, a current level judging unit for comparing one or more switching judgment values set in an area smaller than an overcurrent judgment value with current detected by a current detecting unit to carry out a current level judgment and a time constant changing unit for changing the circuit time constant of the input signal processing circuit in accordance with a judgment result by the current level judging unit.