To regulate the temperature such that a set oil temperature is sustained automatically by controlling the output from a heating means through a control means when a temperature higher or lower than a threshold level is detected, and to stop heating operation automatically as the number of times of heating operation being repeated when the temperature higher or lower than a threshold level is detected and stored in the control means reaches a specified value.

When a temperature detecting means 4 detects a temperature higher or lower than a threshold level corresponding to a set temperature during heating operation of tempura oil, or the like, at an inputted set temperature, a control means (microcomputer) 10 controls the output from a heating means 3 to regulate the temperature such that the set oil temperature is sustained automatically. The control means (microcomputer) 10 has a function for storing the number of times of heating operation being repeated when the temperature higher or lower than a threshold level is detected and stopping the operation automatically when a specified number of times is reached thus ensuring safety.