A similar-information search method includes receiving, with a data computation device, an encrypted feature quantity and an encrypted similarity value from a user terminal device; calculating, with the data computation device, an encrypted distance between an encrypted reference feature quantity and the encrypted feature quantity; determining, with the data computation device, whether the encrypted distance matches the encrypted similarity value; generating, with the data computation device, encrypted reference data that is information obtained by encrypting reference data if it is determined that the encrypted distance matches the encrypted similarity value; and transmitting, with the data computation device, the generated encrypted reference data to the user terminal device.