To calculate quickly a similarity to a query vector even when the number of dimensions of a target vector is large. The similarity calculation system is configured to: acquire a plurality of first target vectors; generate a plurality of second target vectors having a smaller number of dimensions than the plurality of first target vectors by subjecting each of the plurality of first target vectors to predetermined processing; acquire, based on the plurality of second target vectors, a plurality of clusters each including at least one of the plurality of first target vectors and at least one of the plurality of the second target vectors, each of the at least one second target vector corresponding to one of the at least one first target vector; and calculate a similarity between each of the at least one first target vector belonging to one or more clusters selected based on a given query vector having the same number of dimensions as the at least one first target vector, and the given query vector.