To enable that a user can set dimming ratio easily and surely by operation of a wall switch.

In the lighting device equipped with a memory element to memorize set value of the dimming ratio and a power supply detecting part which distinguishes on/off states of a power supply, when a first prescribed on/off operation of a power supply is detected, a command value of the dimming ratio is transferred from a prescribed value set in advance to a dimming ratio setting mode in which a command value is switched from a prescribed value set in advance stepwise or continuously in sequence, and a means is installed to memorize the command value of the dimming ratio as a setting value of a new dimming ratio when a second prescribed on/off operation of the power supply is detected during the period of the dimming ratio setting mode.