A joining method for joining a resin member and a metal member by heating is provided. Joining of the resin member and metal member is performed by heating a joining interface of the resin member and metal member to a temperature in a range of equal to or higher than a decomposition temperature of the resin member and lower than a temperature at which gas bubbles are generated in the resin member and by cooling a surface of the resin member on the opposite side from a joining surface thereof with the metal member to a temperature that is lower than the melting point of the resin member.