Lighting device

In a memory of a lighting device, correspondence relations among an initial output, a target output and time required for reducing brightness from the initial output to the target output are stored in advance. When the initial output and the target output are designated (YES at S1), the time necessary for brightness reduction is specified from the correspondence relation (S3), and the light emission output is reduced at such a change rate that the light emission output has a linear relation with respect to elapsed time from the initial output to the target output in a specified time, on a semi logarithmic graph in which the ordinate is a logarithmic axis representing light emission output and the abscissa is a linear axis representing time (S5).