1. A fluorescent image obtaining device comprising: 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, wherein the imaging unit comprises an imaging element; and color filters that are disposed at a front face of the imaging element, where a plurality of different color filters are disposed in a predetermined arrangement for respective pixels of the imaging element, and wherein an obtaining unit generates an image having only a color component of fluorescence emitted by the fluorescent material marked on the control with the target, from a color image taken by the imaging unit.