A printed wiring board includes a first circuit board having a first surface and a second surface, and a second circuit board having a third surface and a fourth surface and having a mounting area on the third surface of the second circuit board. The first circuit board is laminated on the third surface of the second circuit board such that the first surface of the first circuit board is in contact with the third surface of the second circuit board, the first circuit board includes reinforcing material and has an opening portion exposing the mounting area of the second circuit board, and the first circuit board and the second circuit board are formed such that a ratio H1/h1 is in a range that is greater than 0.75 and smaller than 2.4, where H1 represents a thickness of the first circuit board and h1 represents a thickness of the second circuit board.