To drive an electronic light emitting element by two kinds of luminous flux amount without dispersion without using resistors corresponding to dispersion of forward direction voltage of two kinds of electronic light emitting elements.

This constant current driving circuit is provided with a potential difference generation part 60 provided to generate a potential difference between a first terminal a2 and a second terminal and to switch first and second resistance elements R1 and R2 having resistance values different each other between the first terminal a2 and the second terminal, and control parts 19, 30 and 40 connected to the electronic light emitting elements 10 to control the potential difference between the first terminal and the second terminal in the potential difference generation part 60 to be equal to reference potential Vref. In the constant current driving circuit, the electronic light emitting element is connected to the potential difference generation part 60 in series. When the first signal is inputted, the potential difference generation part 60 is switched to the first resistance element R1. When a second signal is inputted, the potential difference generation part 60 is switched to the second resistance element R2.