In a semiconductor apparatus for controlling a switching power supply including a switching element and a switching operation control circuit, the switching operation of the switching element is controlled as follows: a comparison is made between an output voltage of an I-V converter, which detects the current of a control terminal and converts the current into a voltage, and a reference voltage of predetermined upper and lower limit voltages for detecting a standby state, and the switching operation of the switching element is stopped when the output voltage of the I-V converter is lower than the standby detection lower limit voltage, and the switching operation of the switching element is restarted when the output voltage of the I-V converter is higher than the standby detection upper limit voltage.