A compound semiconductor photovoltaic cell (300, 400, 1100, 1103, 1200, 1300, 1400) comprising: a compound semiconductor substrate being an InP substrate (110, 1110); one or more first photoelectric conversion cells (320, 1120, 1320) made of a first compound semiconductor material and deposited on the compound semiconductor substrate (110, 1110); a bonding layer (330, 1130, 1330) made of a second compound semiconductor material and deposited on the one or more first photoelectric conversion cells (320, 1120, 1320); and one or more second photoelectric conversion cells (160, 1160, 1360) made of a third compound semiconductor material, bonded to the one or more first photoelectric conversion cells (320, 1120, 1320) via the bonding layer (330, 1130, 1330), and disposed on a light incident side of the one or more first photoelectric conversion cells (320, 1120, 1320) in a light incident direction, wherein band gaps of the one or more first photoelectric conversion cells (320, 1120, 1320) and the one or more second photoelectric conversion cells (160, 1160, 1360) decrease as the first and the second photoelectric conversion cells approach from the light incident side toward a back side in the light incident direction, wherein, when a number of the one or more second photoelectric conversion cells (160, 1160, 1360) is one, a band gap of the bonding layer is greater than or equal to the band gap of the one second photoelectric conversion cell, and, when a number of the one or more second photoelectric conversion cells (160, 1160, 1360) is more than one, the band gap of the bonding layer is greater than or equal to the band gap of at least one of the second photoelectric conversion cells (160, 1160, 1360), wherein the first photoelectric conversion cell (320, 1120, 1320), which is disposed in the most front side in the light incident direction among the one or more first photoelectric conversion cells, is an InP based photoelectric conversion cell, wherein the second photoelectric conversion cell, which is disposed in the most back side in the light incident direction among the one or more second photoelectric conversion cells (160, 1160, 1360), is a GaAs based photoelectric conversion cell, and wherein the bonding layer is made of GaInP or GaPSb having a tensile strain relative to the InP substrate (110, 1110). a compound semiconductor substrate being an InP substrate (110, 1110); one or more first photoelectric conversion cells (320, 1120, 1320) made of a first compound semiconductor material and deposited on the compound semiconductor substrate (110, 1110); a bonding layer (330, 1130, 1330) made of a second compound semiconductor material and deposited on the one or more first photoelectric conversion cells (320, 1120, 1320); and one or more second photoelectric conversion cells (160, 1160, 1360) made of a third compound semiconductor material, bonded to the one or more first photoelectric conversion cells (320, 1120, 1320) via the bonding layer (330, 1130, 1330), and disposed on a light incident side of the one or more first photoelectric conversion cells (320, 1120, 1320) in a light incident direction, wherein band gaps of the one or more first photoelectric conversion cells (320, 1120, 1320) and the one or more second photoelectric conversion cells (160, 1160, 1360) decrease as the first and the second photoelectric conversion cells approach from the light incident side toward a back side in the light incident direction, wherein, when a number of the one or more second photoelectric conversion cells (160, 1160, 1360) is one, a band gap of the bonding layer is greater than or equal to the band gap of the one second photoelectric conversion cell, and, when a number of the one or more second photoelectric conversion cells (160, 1160, 1360) is more than one, the band gap of the bonding layer is greater than or equal to the band gap of at least one of the second photoelectric conversion cells (160, 1160, 1360), wherein the first photoelectric conversion cell (320, 1120, 1320), which is disposed in the most front side in the light incident direction among the one or more first photoelectric conversion cells, is an InP based photoelectric conversion cell, wherein the second photoelectric conversion cell, which is disposed in the most back side in the light incident direction among the one or more second photoelectric conversion cells (160, 1160, 1360), is a GaAs based photoelectric conversion cell, and wherein the bonding layer is made of GaInP or GaPSb having a tensile strain relative to the InP substrate (110, 1110).