A fluorescent image obtaining device includes a light source that irradiates light such that a fluorescent material marked on a target in a biological sample lies in a non-excited state and a fluorescent material marked on a control with the target lies in an excited state, and an imaging unit that takes an image including the entire biological sample. The composition comprises three components,, , and. Namely, OLED brightness is controlled not by voltage but by current thereby preventing against the change in OLED brightness due to deterioration of OLED.