A circuit board assembly comprising: a circuit board having an area on which electronic components are mounted, and being provided with a plurality of mounting holes and a through-hole, in a portion of the circuit board other than the area; and a cover that surrounds and supports the circuit board, the cover covering the circuit board with a clearance interposed between the cover and a portion of the circuit board, which includes the area, wherein the cover includes a first cover to cover a first surface of the circuit board and a second cover to cover a second surface of the circuit board, and the cover is provided, on its inner surface, with a suppression portion passing through the through-hole of the circuit board, projecting from at least one of the first cover and the second cover, and configured to suppress the inner surface from approaching the area when external pressure is applied to the cover, characterised in that the first cover is made of synthetic resin and has a circuit board attachment portion and a cable terminal cover portion integrally joined to a base end of the circuit board attachment portion, a plurality of board-resting portions which are arranged in a width direction on a surface of the circuit board attachment portion at a central portion thereof are each provided with a mounting projection, the circuit board is placed on the board-resting portions, and leading ends of the mounting projections pass through the mounting holes and are heated in a state where the leading ends project from the circuit board, and melted to cover the mounting holes and their peripheries, and the melted leading ends are then solidified to adhere to the surface of the circuit board, which faces the second cover. a circuit board having an area on which electronic components are mounted, and being provided with a plurality of mounting holes and a through-hole, in a portion of the circuit board other than the area; and a cover that surrounds and supports the circuit board, the cover covering the circuit board with a clearance interposed between the cover and a portion of the circuit board, which includes the area, wherein the cover includes a first cover to cover a first surface of the circuit board and a second cover to cover a second surface of the circuit board, and the cover is provided, on its inner surface, with a suppression portion passing through the through-hole of the circuit board, projecting from at least one of the first cover and the second cover, and configured to suppress the inner surface from approaching the area when external pressure is applied to the cover, characterised in that the first cover is made of synthetic resin and has a circuit board attachment portion and a cable terminal cover portion integrally joined to a base end of the circuit board attachment portion, a plurality of board-resting portions which are arranged in a width direction on a surface of the circuit board attachment portion at a central portion thereof are each provided with a mounting projection, the circuit board is placed on the board-resting portions, and leading ends of the mounting projections pass through the mounting holes and are heated in a state where the leading ends project from the circuit board, and melted to cover the mounting holes and their peripheries, and the melted leading ends are then solidified to adhere to the surface of the circuit board, which faces the second cover.