A concentric optical system usable as either an imaging optical system or an ocular optical system, which enables a clear image to be obtained at a field angle of up to about 90.degree. and with a pupil diameter of up to about 10 millimeters with substantially no chromatic aberration. The concentric optical system includes a first optical component having a first semitransparent reflecting surface (2), and a second optical component having a second semitransparent reflecting surface (3). The first and second semitransparent reflecting surfaces (2 and 3) have respective centers of curvature disposed at approximately the same position (1). The first and second optical components are different in dispersion from each other. The first and second semitransparent reflecting surfaces (2 and 3) are arranged so that a bundle of light rays passing through the first semitransparent reflecting surface (2) is reflected by the second semitransparent reflecting surface (3), and the bundle of light rays reflected by the second semitransparent reflecting surface (3) is reflected by the first semitransparent reflecting surface (2) and then passes through the second semitransparent reflecting surface (3). The optical system satisfies the condition of 0.2