An endoscope system (10, 200, 300) comprising: a light source device that is configured to generate illuminatior light to irradiate an observation object and is configured to to control an optical spectrum of the illumination light; an image sensor (48, 304) which includes a blue pixel receiving light in a blue wavelength band, a green pixel receiving light in a green wavelength band, a red pixel receiving light in a red wavelength band, and a specific pixel receiving at least light in a blue wavelength band and a green wavelength light, and is configured to image the observation object by reflected light of the illumination light from the observation object; an imaging distance calculator which is configured to calculate an imaging distance which is a distance between the image sensor and the observation object; and a light source controller (32, 210) which is configured to increase a component of the blue wavelength band or the green wavelength band included in the illumination light according to the imaging distance, the endoscope system (10, 200, 300) further comprising: a demosaic processor, the endoscope system being characterised in that the demosaic processor is configured to apply a first demosaic process performed with use of an image signal from the white pixel as a green image signal and a second demosaic process performed with use of an image signal from the white pixel as a blue image signal, the demosaic processor being configured to selectively apply the first demosaic process and the second demosaic process according to the image distance to an image signal which the image sensor outputs, wherein the signal value of the white pixel is used as the green image signal of the white pixel position in the first demosaic process, and is used as the blue image signal of the white pixel position in the second demosaic process. a light source device that is configured to generate illuminatior light to irradiate an observation object and is configured to to control an optical spectrum of the illumination light; an image sensor (48, 304) which includes a blue pixel receiving light in a blue wavelength band, a green pixel receiving light in a green wavelength band, a red pixel receiving light in a red wavelength band, and a specific pixel receiving at least light in a blue wavelength band and a green wavelength light, and is configured to image the observation object by reflected light of the illumination light from the observation object; an imaging distance calculator which is configured to calculate an imaging distance which is a distance between the image sensor and the observation object; and a light source controller (32, 210) which is configured to increase a component of the blue wavelength band or the green wavelength band included in the illumination light according to the imaging distance, the endoscope system (10, 200, 300) further comprising: a demosaic processor, the endoscope system being characterised in that the demosaic processor is configured to apply a first demosaic process performed with use of an image signal from the white pixel as a green image signal and a second demosaic process performed with use of an image signal from the white pixel as a blue image signal, the demosaic processor being configured to selectively apply the first demosaic process and the second demosaic process according to the image distance to an image signal which the image sensor outputs, wherein the signal value of the white pixel is used as the green image signal of the white pixel position in the first demosaic process, and is used as the blue image signal of the white pixel position in the second demosaic process.