To provide a detector of a remaining amount of ink capable of reducing wrong detection factors such as a sensor, a light guide, reflection light and the like incorporated in an apparatus.

Sensor output is detected by varying power supplied to the sensor to the sensor output while the power supplied to the sensor is being varied, and variation of the supplied power is set by the detected output signal. As the variation means, a D.C. power source is subjected to PWM control. In addition, the D.C. power subjected to PWM control made to pass through an LPF, and thereafter supplied to the sensor. The duty ratio of PWM is changed in time-sharing to be able to detect a plurality of sensors with the same power source and the same detection means, and the output thereof is detected.