The present invention includes an activating step S2 of activating, by irradiating a first substrate surface of a first substrate and a second substrate surface of a second substrate with particles, the second substrate surface and the first substrate surface, and a bonding step S4 of bonding the second substrate and the first substrate together by bringing the second substrate surface and the first substrate surface into contact with each other after a temperature difference between a temperature of the first substrate and a temperature of the second substrate becomes equal to or lower than a predetermined value. According to this bonding method, warpage occurring in a bonded substrate obtained can be further reduced compared with other bonding methods of bonding both substrates before the temperature difference between the temperature of the first substrate and the temperature of the second substrate becomes equal to or lower than a predetermined value.