To provide a sterilizing apparatus capable of continuously carrying out sterilization without causing change in sterilization, cooling temperature and flow rate when the sterilizing temperature, cooling temperature and flow rate are previously set with water and then, water is replaced with a actual solution to be treated.

This sterilizing apparatus comprises a heat exchanger 1 on heating side of carrying out heat sterilization of a solution to be treated, a change over valve A 4 for changing over between sterilized solution 2 to be treated and a unsterilized solution to be treated, a hold pipe 5 for temporally retaining the sterilized solution to be treated from the change over valve A 4, a heat exchanger 6 on cooling side for cooling the solution to be treated from the hold pipe, a change over valve B 7 for taking out the cooled solution to be treated and heat exchanger 12 on divert cooling side for cooling and discharging unsterilized solution to be treated from diversion side of the change over valve A 4. In this case, the change over valve A 4 is formed as a four-way valve and the change over valve B 7 is formed as three-way valve and piping 9 for connecting either one port of the four-way valve to the diversion side of three-way valve is provided and water is previously fed thereto to set sterilizing temperature, cooling temperature and flow rate, etc., and then, water can continuously be replaced with a solution to be treated in the same conditions.