A simple method has been developed for manufacturing a thin film superconducting quantum interferometer (SQI) with ultralow inductance (_10_13 H). Current-voltage and voltage-field characteristics of the SQI are presented. The basic design equations are obtained and confirmed experimentally. The SQI has been used for the first time to determine the penetration depth of a magnetic field into a film of 50% In-50% Sn alloy.