A wide-angle imaging device suitable for a monitor area of about 180 degrees. A first reflection mirror (1) is provided that has, around the rotation center axis (6) of a rotary symmetrical body, a reflection surface having an approximately ±90-degree convex shape with respect to a reference optical axis direction, an image forming lens (2) that has a principal point (7) on the rotation center axis of the first reflection mirror (1) and forms the image of a reflection beam from the first reflection mirror (1) and an imaging element (3) are disposed, and an object within approximately ±90 degrees around the rotation center axis of the first reflection mirror (1) is imaged.