To provide single-sided circuit boards for composing a multilayer circuit board having high electrical reliability.

A plurality of bottlenecks 18a are provided to the side walls of via holes 18 of the single-sided circuit boards A, B1, B2, B3, and B4, so that the contacting surface of an insulating board 10 with the via hole 18 can be increased in area, and the adhesion of the insulating board to the via hole 18 can be improved. Stress generated when the single-sided circuit boards A, B1, B2, B3, and B4 are laminated and bonded together by pressure can be relaxed. When the single-sided circuit boards A, B1, B2, B3, and B4 are pressed (pressure-bonding), stress conducted to the inside and outside of the via hole 18 is buffered by the bottlenecks 18b, and the attenuated stress is conducted as a whole, so that cracking and fracture hardly occur in the multilayer circuit board.