PURPOSE: To measure flow rate distribution easily and rapidly without decomposing a pipe bundle and channels, by equipping thermocouples on the outside of respective pipe at constant intervals and by measuring an electromotive force difference which corresponds to each flow rate.

CONSTITUTION: Thermocouples 6 and 7 are equipped at constant intervals at the outside of respective pipes 1 forming a pipe bundle. An electromotive force difference between the thermocouples 6 and 7 varies with temperature distribution corresponding to the fluid flow rate of each pipe 1. Therefore, the electromotive force difference between both the thermocouples 6 and 7 is detected and, after constant processing corresponding to the kind of the fluid is performed through a switching device 10, displayed on a meter 8, so that the flow rate distribution of the pipe bundle is measured easily and rapidly without decomposing the pipe bundle and channels.