PROBLEM TO BE SOLVED: To provide a light amount adjustment device allowing saving of sensor energy consumption, reduction of a circuit mounting area and reduction of a cost burden by using a single light-amount adjustment circuit to adjust light amounts of a plurality of sensors.SOLUTION: A light amount adjustment device 20 includes a plurality of sensors each consists of a sensor light emission part 22 and a sensor light reception part 23 and adjusts the light amounts of the plurality of sensors (a sensor group 21). The light amount adjustment device comprises: selector circuits 24 and 26 which sequentially select one sensor from the sensor group 21; a light amount adjustment circuit 28 which adjusts a drive current value of each selected sensor so that a light reception level of the sensor light reception part 23 is at a constant level; and a microcomputer 25 which stores the adjusted drive current value of each sensor. The microcomputer 25 determines the maximum value among the drive current values of the sensors stored in the microcomputer 25 as a default current value of the sensor group 21 and drives the sensor group 21 based on the determined default current value.
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