An imaging device (1) including; a fluctuation correcting section (13) for correcting fluctuation of the input/output characteristics of the imaging element (4), and the linearizing section (14) for converting the signals outputted from the imaging element (4) into the state where the output signals are uniformly converted by one conversion characteristic. The fluctuation correcting section (13) is provided with a first correcting section (13a) for correcting fluctuation based on a computing equation obtained by modeling a plurality of kinds of conversion characteristic, and a second correcting section (13b) for correcting the output signals in a region close to a switch point of a plurality of kinds of conversion characteristics among the output signals whose fluctuations are corrected by the first correcting section (13a), by using model equations of two characteristics on the sides of the switch point, so that the output signal overlaps the characteristic of the imaging element (4).