A magnesium-based composite member is provided with a through hole through which a fastening member for attachment to a fixing target is to be inserted. A substrate is provided with a substrate hole through which the fastening member is to be inserted, and made of a composite material which is a composite of SiC and a matrix metal which is any of magnesium and a magnesium alloy. A receiving portion is attached to the substrate and made of a metal material different from the matrix metal. The receiving portion is provided with a receiving portion hole through which the fastening member is to be inserted, and at least a part of an inner circumferential surface of the through hole is formed from an inner circumferential surface of the receiving portion hole.