An object of the present invention is enabling to correct a color mixture of color components that occurs when color lights of plural wavelength bands are simultaneously received and enabling to acquire an image excellent in color reproducibility. An observation apparatus according to the present invention has a capsule endoscope (2) that has light-emitting units (8a to 8c) and an imaging unit (9), a receiving device (3) that has an image processing unit (14), and an image display device (4) that displays an in-vivo image. The light-emitting units (8a to 8c) emit light of RGB color lights, and a color chart (7) reflects each RGB color light onto the imaging unit (9). The imaging unit (9) has color filters of a plurality of colors corresponding to the respective RGB color lights to simultaneously capture an in-vivo image and a chart image. The image processing unit (14) calculates in advance an inverse matrix M -1 of the color-mixture matrix M indicative of a color-mixture state of the color lights to be received and other color lights correspondingly to these color filters, and multiplies a light-receiving-amount value of each unit pixel group forming the in-vivo image captured by the imaging unit (9) by the inverse matrix M -1 to correct the color-mixture state.
