A current diffusion bonding apparatus (1) includes upper and lower electrodes (11, 12), which sandwich members to be bonded (M, M) and which are electrically conductible with the members to be bonded (M, M); a power supply unit (20), which supplies a current to the electrodes (11, 12); and a pressurizing unit (30), which applies a pressure to bonding surfaces S. If a temperature T detected by a temperature sensor (45) is a first set temperature T1 or lower, the pressurizing unit (30) applies a pressure to the bonding surfaces S while restricting the displacement of the members to be bonded (M, M), and if the temperature T exceeds the first set temperature T1, the pressurizing unit (30) applies a pressure based on the elastic force of a spring (35d), which elastically deforms according to the displacement of the members to be bonded (M, M), to the bonding surfaces S.