An imaging device comprising two imaging optical systems each of the imaging optical systems including a wide-angle lens having an angle of view wider than 180 degrees, and an imaging sensor configured to image an image by the wide-angle lens, so as to obtain an image in a solid angle of 4π radian by synthesizing the images by the respective imaging optical systems, wherein the wide-angle lens of each of the imaging optical systems includes, in order from an object side to an image side, a front group having a negative power, a reflection surface and a back group having a positive power, and is configured to bend an optical axis of the front group by the reflection surface at 90 degrees toward the back group, the reflection surface is formed by a prism having an inclined surface as an internal reflection surface; the imaging sensor is provided in a substrate having a predetermined circuit and a size which is larger than that of the imaging sensor, the two imaging optical systems are combined such that the front groups face opposite directions to each other with the optical axes of the front groups being aligned and the back groups face opposite directions to each other, where a surface including the aligned optical axes of the front groups of the two wide-angle lenses, which is orthogonal to the optical axis of the back group, is an S-surface, and a distance between the optical axes of the two back groups is D and a distance between the S-surface and a substrate surface of the substrate is L, and where an intersection line by combination of conical surfaces formed by maximum angle of view light beams of the wide-angle lenses around the optical axes of the front groups of the respective imaging optical systems and a plane parallel to the substrate surface of the substrate is X1 relative to one wide-angle lens and X2 relative to the other wide-angle lens, the distances D, L and the size and a shape of the substrate are set according to a maximum angle of view F of the wide-angle lens such that corner portions of the substrate do not locate outside an area surrounded by the intersection lines X1, X2, characterized in that: the front group constitutes, in order from an object side to an image side, a meniscus lens having a negative refractive power, an aspheric surface meniscus lens having a negative refractive power and a negative meniscus lens; an aperture stop is positioned between the reflection surface and the back group; the back group constitutes, in order from an object side to an image side: a biconvex lens having a positive refractive power; a cemented lens of a biconvex lens having a positive refractive power; and a biconcave lens having a negative refractive power, and a biconvex lens having a positive refractive power; and a distance from a most object side surface of the front group to the internal reflection surface LF, and a distance from the internal reflection surface to a most image side surface of the back group LR satisfy the following condition: LF < LR the front group constitutes, in order from an object side to an image side, a meniscus lens having a negative refractive power, an aspheric surface meniscus lens having a negative refractive power and a negative meniscus lens; an aperture stop is positioned between the reflection surface and the back group; the back group constitutes, in order from an object side to an image side: a biconvex lens having a positive refractive power; a cemented lens of a biconvex lens having a positive refractive power; and a biconcave lens having a negative refractive power, and a biconvex lens having a positive refractive power; and a distance from a most object side surface of the front group to the internal reflection surface LF, and a distance from the internal reflection surface to a most image side surface of the back group LR satisfy the following condition: LF < LR