A capsule endoscope includes a flexible substrate which is integrally formed by disposing an illumination substrate section, a first wiring substrate section, an imaging element substrate, a second wiring substrate section, and a signal-processing substrate section in a row in sequence and an illumination control circuit which includes an illumination control signal output unit and an illumination driving unit, wherein the light-emitting elements are LEDs, wherein the illumination driving unit is disposed on the imaging element substrate section or the illumination substrate section, and wherein the illumination driving unit includes a transistor array which is formed by a plurality of transistors, the plurality of transistors corresponding to each of the light-emitting elements provided in the illumination unit and generating illumination currents in accordance with the illumination control signal.