Abstract: An ultrasonic delay line of a construction which is made up of: a casing having therein a delay medium accommodating section to accommodate therein a delay medium and a terminal accommodating section to accommodate therein planar metal terminals; and a cover to tightly close the casing, in which the terminal accommodating section has a plurality of projections to fix the planar metal terminals, a partition frame is provided between the terminal accommodating section and the delay medium accommodating section to separate both accommodating sections, the delay medium is accommodating in the delay medium accommodating section, the base part of the planar metal terminal is positioned and housed by means of projections in the terminal accommodating section, and one end of a lead wire, the other end of which has been connected with a transducer provided on the said surface of the delay medium, is connected with the base part of the planar metal terminal.