An assembly of dissimilar material members comprising: a first joining-target member in a platy shape made of resin, the first joining-target member including a hole extending through the first joining-target member; a second joining-target member in a platy shape made of metal, the second joining-target member including a portion that faces the hole and an outer circumference of the hole; and a rivet including: a shaft-shaped portion disposed within the hole, the shaft-shaped portion having an axial direction along a plate thickness direction of the first joining-target member; and a head integral with a first end in the axial direction of the shaft-shaped portion, the head being disposed outside the hole, wherein the rivet is made of metal, and the rivet is configured such that a brim portion defining a part of the head is in contact with a surface of the first joining-target member, an end of a second end side in the axial direction of the shaft-shaped portion is joined to the second joining-target member via a welded portion, and the brim portion holds the first joining-target member between the brim portion and the second joining-target member, the shaft-shaped portion includes: a shaft in a pillar shape extending from a center of the head; an enlarged diameter portion which extends from the shaft and having a diameter dimension set to be greater than a diameter dimension of the shaft; and a punching portion joined to the second joining-target member via the welded portion, the hole includes: a small-diameter hole portion set to be formed at an outer circumference of the shaft, the small-diameter hole portion having an inner diameter dimension equal to the diameter dimension of the enlarged diameter portion; and a large-diameter hole portion formed at an outer circumference of the punching portion, the large-diameter hole portion having an inner diameter dimension greater than the diameter dimension of the enlarged diameter portion, and a gap is set in a radial direction of the shaft-shaped portion through an entire circumference between an inner circumferential surface of the hole and an outer circumferential surface of the shaft-shaped portion. a first joining-target member in a platy shape made of resin, the first joining-target member including a hole extending through the first joining-target member; a second joining-target member in a platy shape made of metal, the second joining-target member including a portion that faces the hole and an outer circumference of the hole; and a rivet including: a shaft-shaped portion disposed within the hole, the shaft-shaped portion having an axial direction along a plate thickness direction of the first joining-target member; and a head integral with a first end in the axial direction of the shaft-shaped portion, the head being disposed outside the hole, wherein the rivet is made of metal, and the rivet is configured such that a brim portion defining a part of the head is in contact with a surface of the first joining-target member, an end of a second end side in the axial direction of the shaft-shaped portion is joined to the second joining-target member via a welded portion, and the brim portion holds the first joining-target member between the brim portion and the second joining-target member, the shaft-shaped portion includes: a shaft in a pillar shape extending from a center of the head; an enlarged diameter portion which extends from the shaft and having a diameter dimension set to be greater than a diameter dimension of the shaft; and a punching portion joined to the second joining-target member via the welded portion, the hole includes: a small-diameter hole portion set to be formed at an outer circumference of the shaft, the small-diameter hole portion having an inner diameter dimension equal to the diameter dimension of the enlarged diameter portion; and a large-diameter hole portion formed at an outer circumference of the punching portion, the large-diameter hole portion having an inner diameter dimension greater than the diameter dimension of the enlarged diameter portion, and a gap is set in a radial direction of the shaft-shaped portion through an entire circumference between an inner circumferential surface of the hole and an outer circumferential surface of the shaft-shaped portion.