In the endoscope apparatus, a signal picked up by a CCD having a color separation filter is separated into a first luminance signal and a first color difference signal by a Y / C separation circuit, and then 3 by a first and second matrix circuit. The signal is converted into the primary color signal and the second color difference signal, and the signal intensity ratio of the three primary color signals is calculated by a signal intensity ratio calculation circuit interposed therebetween. The first luminance signal and the second color difference signal are converted by color separation of the first luminance signal according to the signal intensity ratio by the third matrix circuit.内視鏡装置において、色分離フィルタを備えたＣＣＤにより撮像された信号は、Ｙ／Ｃ分離回路により第１輝度信号と第１色差信号に分離された後、第１及び第２マトリクス回路により３原色信号と第２色差信号に変換されると共に、間に介挿された信号強度比算出回路により３原色信号の信号強度比が算出される。第１輝度信号と第２色差信号は、第３マトリクス回路により、信号強度比に応じて第１輝度信号に対する色分離を施した変換を行う。
