An intensity controlling circuit device can correct variation in intensity of light beams, due to tolerance occurred in each of a plurality of LED-array chips, emitted by LEDs provided in each of the LED-array chips. The intensity controlling circuit device is connected to at least one LED-array chip comprising a plurality of LEDs and slave transistors corresponding to each of the LEDs. The intensity controlling circuit device comprises an intensity controlling circuit connected to the respective LED-array chip. The intensity controlling circuit comprises a first transistor provided between a power source and a constant current generating unit so as to supply a current to the LED-array chip, and an intensity adjusting unit having a second transistor connected to the first transistor in parallel and a controlling unit for controlling the on/off state of the second transistor. An output of the intensity controlling circuit is connected to each of the slave transistors provided in the LED-array chip, and the second transistor is turned on/off by the controlling unit so that a current flowing in each of the LEDs is adjusted to a predetermined value.