To provide a throttling calorimeter for drastically improving efficiency without need for removing the flange of the throttling calorimeter.

A throttling calorimeter consists of a fixing nozzle 3 in a circular plate shape that has a plurality of through holes 2 and at the same time fixes the inside of a pipe 22 in a blocked state, a rotary nozzle 1 that is inserted into the center of the fixing nozzle 3, a shaft 4 with nut for rotating the rotary nozzle 1, a pressure gauge 30 that is installed at the upstream side of the fixing nozzle 3, and a thermocouple 15 that is installed in an inflation chamber 34 at the downstream side of the fixing nozzle 3. One end of the shaft 4 is inserted into a square hole 12 of the above rotary nozzle 1, the other end is inserted into the pipe 22 via a nut 7 with scale, the rotary nozzle 1 can be rotated to a specific position by rotating the shaft 4, and steam passing through the through hole 2 can be emitted in the axial direction of the throttling calorimeter when the center of the through hole 2 of the fixing nozzle 3 coincides with the nozzle hole 14 of the above rotary nozzle 1.