A connector for connecting a first circuit board (11, 41, 61) comprising a plurality of openings and having at each of plural openings a first contact portion (16A, 16B) that is bendable and a second circuit board (21, 51, 71) comprising a plurality of openings and having at each of plural openings a second contact portion (26A, 26B) that is bendable, the connector being characterized by comprising: a first connector portion (32, 32A, 82, 82A, 92) extending along an XY plane, wherein in the first connector portion (32, 32A, 82, 82A, 92) plural projections (35, 35B, 85, 85A, 95) project on the surface of a base plate (34, 34A, 84, 94) facing in a +Z direction; and a second connector portion (33, 93) formed of a fitting plate in which plural fitting holes (37, 97) corresponding to the plural projections are formed, wherein at least either the projections or the fitting holes have elasticity, and wherein the projections and the fitting holes are configured such that, when the plural projections of the first connector portion are fitted through the openings of the first and second circuit boards into the plural fitting holes of the second connector portion as catching the first contact portion of the first circuit board and the second contact portion of the second circuit board with the first and second contact portions facing and being overlapped on each other, the first contact portion of the first circuit board and the second contact portion of the second circuit board are elastically pressed against each other and contacted to each other to establish electrical connection therebetween in a space between a lateral surface of the plural projections and an inner surface of the plural fitting holes, wherein the first contact portion (16A, 16B) is formed on a surface of a first protruding piece protruding in each of the plural openings from the first circuit board and having insulation properties, wherein the second contact portion (26A, 26B) is formed on a surface of a second protruding piece protruding in each of the plural openings from the second circuit board and having insulation properties, and wherein when the plural projections of the first connector portion are fitted in the plural fitting holes of the second connector portion, one of a bottom surface of the first protruding piece and a bottom surface of the second protruding piece is in contact with the lateral surface of the plural projections, while the other of the bottom surface of the first protruding piece and the bottom surface of the second protruding piece is in contact with the inner surface of the plural fitting holes. a first connector portion (32, 32A, 82, 82A, 92) extending along an XY plane, wherein in the first connector portion (32, 32A, 82, 82A, 92) plural projections (35, 35B, 85, 85A, 95) project on the surface of a base plate (34, 34A, 84, 94) facing in a +Z direction; and a second connector portion (33, 93) formed of a fitting plate in which plural fitting holes (37, 97) corresponding to the plural projections are formed, wherein at least either the projections or the fitting holes have elasticity, and wherein the projections and the fitting holes are configured such that, when the plural projections of the first connector portion are fitted through the openings of the first and second circuit boards into the plural fitting holes of the second connector portion as catching the first contact portion of the first circuit board and the second contact portion of the second circuit board with the first and second contact portions facing and being overlapped on each other, the first contact portion of the first circuit board and the second contact portion of the second circuit board are elastically pressed against each other and contacted to each other to establish electrical connection therebetween in a space between a lateral surface of the plural projections and an inner surface of the plural fitting holes, wherein the first contact portion (16A, 16B) is formed on a surface of a first protruding piece protruding in each of the plural openings from the first circuit board and having insulation properties, wherein the second contact portion (26A, 26B) is formed on a surface of a second protruding piece protruding in each of the plural openings from the second circuit board and having insulation properties, and wherein when the plural projections of the first connector portion are fitted in the plural fitting holes of the second connector portion, one of a bottom surface of the first protruding piece and a bottom surface of the second protruding piece is in contact with the lateral surface of the plural projections, while the other of the bottom surface of the first protruding piece and the bottom surface of the second protruding piece is in contact with the inner surface of the plural fitting holes.