To provide a testing device for easily testing a differential distribution type heat sensor.

A connection part 30 of the testing device is connected to a connection part 10 on the side of the heat sensor and an adjusting screw 34 is threaded into an adjusting chamber 33 at a predetermined speed by an electric driver 50. Thus, an air is filled from a pressure filling part 31 via an inlet 13 into an air pipe 1. Air pressure in the air pipe 1 is detected via a pressure detection part 32 by a pressure sensor 41. A control part 44 controls the speed of the electric driver 50 so that the air pressure detected by the pressure sensor 41 is at a preset rate of rise. With the lapse of a specified time, if a signal OUT for a fire is output from a fire determination part of the heat sensor, the operation of the heat sensor is determined to be normal.