A method for bonding composite materials together, wherein a first composite material (12, 12', 12'', 12''') and a second composite material (14, 14', 14", 14''') prepared by impregnating reinforced fibers with thermosetting resins are bonded together by heating to heat-cure the first and second composite materials (12, 12', 12", 12"', 14, 14', 14'', 14"'), and at least prescribed regions of the first and second composite materials (12, 12', 12", 12"', 14, 14', 14'', 14''') assume a softened state, which is a state before the thermosetting resins are heat-cured, a cured state, which is a state after the thermosetting resins are heat-cured, or a semi-cured state, which is a state between the softened state and the cured state; the method comprising: a first curing preparation step, wherein a first bonding region of the first composite material (12, 12', 12'', 12''') to be bonded to the second composite material (14, 14', 14", 14''') is prepared to be maintained in a softened state; a first curing step performed after the first curing preparation step, wherein a first non-bonding region (12b, 12b'), which is a region other than the first bonding region (12a, 12a', 12a''), is placed in the cured state by heating; a first semi-curing preparation step, wherein the first bonding region (12a, 12a', 12a") is placed in a heatable state; a first semi-curing step performed after the first semi-curing preparation step, wherein the first bonding region (12a, 12a', 12a") is placed in the semi-cured state by heating; a contact pressure step, wherein the first bonding region ( 12a, 12a', 12a"), having assumed the semi-cured state in the first semi-curing step, is pressed in contact with a second bonding region (14a, 14a', 14a") of the second composite material (14, 14', 14'', 14''') to be bonded with the first composite material (12, 12', 12'', 12"'), the second bonding material assuming the softened state or the semi-cured state; and a heat-bonding step, wherein the first and second bonding regions (12a, 12a', 12a", 14a, 14a', 14a"), having been brought into contact and pressed in the contact pressure step, are placed in the cured state by heating. at least prescribed regions of the first and second composite materials (12, 12', 12", 12"', 14, 14', 14'', 14''') assume a softened state, which is a state before the thermosetting resins are heat-cured, a cured state, which is a state after the thermosetting resins are heat-cured, or a semi-cured state, which is a state between the softened state and the cured state; the method comprising: a first curing preparation step, wherein a first bonding region of the first composite material (12, 12', 12'', 12''') to be bonded to the second composite material (14, 14', 14", 14''') is prepared to be maintained in a softened state; a first curing step performed after the first curing preparation step, wherein a first non-bonding region (12b, 12b'), which is a region other than the first bonding region (12a, 12a', 12a''), is placed in the cured state by heating; a first semi-curing preparation step, wherein the first bonding region (12a, 12a', 12a") is placed in a heatable state; a first semi-curing step performed after the first semi-curing preparation step, wherein the first bonding region (12a, 12a', 12a") is placed in the semi-cured state by heating; a contact pressure step, wherein the first bonding region ( 12a, 12a', 12a"), having assumed the semi-cured state in the first semi-curing step, is pressed in contact with a second bonding region (14a, 14a', 14a") of the second composite material (14, 14', 14'', 14''') to be bonded with the first composite material (12, 12', 12'', 12"'), the second bonding material assuming the softened state or the semi-cured state; and a heat-bonding step, wherein the first and second bonding regions (12a, 12a', 12a", 14a, 14a', 14a"), having been brought into contact and pressed in the contact pressure step, are placed in the cured state by heating. a first curing preparation step, wherein a first bonding region of the first composite material (12, 12', 12'', 12''') to be bonded to the second composite material (14, 14', 14", 14''') is prepared to be maintained in a softened state; a first curing step performed after the first curing preparation step, wherein a first non-bonding region (12b, 12b'), which is a region other than the first bonding region (12a, 12a', 12a''), is placed in the cured state by heating; a first semi-curing preparation step, wherein the first bonding region (12a, 12a', 12a") is placed in a heatable state; a first semi-curing step performed after the first semi-curing preparation step, wherein the first bonding region (12a, 12a', 12a") is placed in the semi-cured state by heating; a contact pressure step, wherein the first bonding region ( 12a, 12a', 12a"), having assumed the semi-cured state in the first semi-curing step, is pressed in contact with a second bonding region (14a, 14a', 14a") of the second composite material (14, 14', 14'', 14''') to be bonded with the first composite material (12, 12', 12'', 12"'), the second bonding material assuming the softened state or the semi-cured state; and a heat-bonding step, wherein the first and second bonding regions (12a, 12a', 12a", 14a, 14a', 14a"), having been brought into contact and pressed in the contact pressure step, are placed in the cured state by heating.