Regarding electronic component mounting in which an electronic component having plural solder bumps for external connection on its lower surface is mounted on a board, in an electronic component mounting operation of previously measuring the height position of solder paste on the board on which the solder paste has been printed, and mounting the electronic component on the board on which the solder paste has been printed by a loading head, whether the transfer of the solder paste to the solder bumps is necessary or not is judged on the basis of the measurement result of the height of the solder paste. In case that it is judged that the transfer is necessary, the transfer of the solder paste is executed, and thereafter the electronic component is mounted on the board. Hereby, it is possible to prevent the poor joint in case that a thin-sized semiconductor package which causes easily warp deformation is mounted on the board by solder-joint.