To provide a film mirror which does not cause a distortion on a mirror face and suppresses deterioration of a regular reflectance of the mirror face even when used under a severe environment for a long term as a film mirror for solar power generation, and which is light and flexible, reduced in production cost, can be formed in large area and mass-produced, is excellent in durability, and has an excellent regular reflectance against sunlight; and to provide a manufacturing method of the film mirror and a reflection device for solar power generation including the film mirror.

The film mirror is formed by laminating a first stretched film and a second stretched film via an adhesive layer while sandwiching a silver reflection layer provided on the first stretched film. The main stretching directions of the first and second stretched films cross each other, and the crossing angle is 45° or more and 90° or less.