Abstract: It is an object of the present invention to provide an optical sensor that has a simple structure and which yet enables positive detection of the inclination of an object of interest, and also to provide a process for producing the same. The improved sensor comprises a light-emitting element, a light-receiving element, a body having an inclined surface formed between the two elements, a lid fitted over the body, and a sphere placed between the body and the lid in such a way that it is capable of movement down the inclined surface. In the process, a light-emitting device and a light-receiving device, both subjected to primary molding, are respectively set between the lower and the middle part of a split mold and between the middle and the upper part of the mold; secondary molding is then performed by injecting an opaque resin into the cavity defined by the lower, middle and upper parts of the mold.