The method for forming a quantum dot according to the present invention comprises the step of forming an oxide in a dot-shape on the surface of a semiconductor substrate 10, the step of removing the oxide to form a concavity 16 in the position from which the oxide has been removed, and the step of growing a semiconductor layer 18 on the semiconductor substrate with the concavity formed in to form a quantum dot 20 of the semiconductor layer in the concavity. The concavity is formed in the semiconductor substrate by forming the oxide dot in the surface of the semiconductor substrate and removing the oxide, whereby the concavity can be formed precisely in a prescribed position and in a prescribed size. The quantum dot is grown in such a concavity, whereby the quantum dot can have good quality and can be formed in a prescribed position and in a prescribed size.