There is provided a method for producing a multijunction solar cell having four-junctions, the method allowing the area of a device to be increased. On a nucleation site formed on a substrate 2, is grown a semiconductor 2a comprising the same material as the substrate 2 in the shape of a wire. On the semiconductor 2a, are successively grown semiconductors 3, 4, 5, and 6 with a narrower band gap in the shape of a wire. The semiconductor 3 may be directly grown in the shape of a wire on the nucleation site formed on the substrate 2. It is preferred to form the nucleation site by forming an amorphous SiO2 coating 8a on the substrate 2 and etching a part of the amorphous SiO2 coating 8a. Further, it is preferred to form an insulating film 8 in the region except the nucleation sites on the substrate 2 by allowing the amorphous SiO2 coating 8a to remain therein. The semiconductor 2a is GaP; the semiconductor 3 is Al0.3Ga0.7As; the semiconductor 4 is GaAs; the semiconductor 5 is In0.3Ga0.7As; and the semiconductor 6 is In0.6Ga0.4As.