To provide a heat supply system capable of early and properly performing inspection work of respective parts after trial operation.

This heat supply system HS has a control means 4 performing heated heating medium circulating operation for making a heating medium heated by a heat source machine 1 circularly flow in the whole area or the substantially whole area of heating medium circulating pipe systems 3A to 3C, by putting the heat source machine 1 and a circulating pump P in an operation state, when performing predetermined operation in an operation means 40. The control means 4 performs heat radiating heating medium circulating operation for making the heating medium circularly flow in the whole area or the substantially whole area of the heating medium circulating pipe systems 3A to 3C without heating, by operating the circulating pump P in a state of stopping operation of the heat source machine 1, after performing the heated heating medium circulating operation.