The number of thermal sensors in an imaging device that requires temperature measurement is reduced. The imaging device includes: a lens array (112) including lenses; an imaging element (122) provided at a predetermined distance from the lens array (112) and having imaging areas respectively corresponding to the lenses; a light-shielding wall (113) which partitions a space between the lens array and the imaging element so as to prevent light entering each of the lenses from reaching the imaging areas different from a corresponding one of the imaging areas; an imaging signal input unit (133) configured to generate an imaging signal by digitalizing an electric signal provided by the imaging element; and a temperature estimation unit (143) configured to calculate, from the imaging signal, a length of an image of the light-shielding wall projected on an imaging plane of the imaging element, and to estimate a temperature using the calculated length of the image of the light-shielding wall.