To provide a contact angle measurement device that can predict a wet state of combustion ashes in a boiler furnace by heating the interior of a chamber and cooling a pedestal, and a prediction method for behavior of combustion ashes in a boiler furnace.

There is provided a contact angle measurement device 1 which measures the contact angle of a sample 7 placed on a pedestal 6 provided in a container 4. The contact angle measurement device includes heating means 8 of heating the sample in the container; cooling means 9 of cooling the pedestal; first temperature detection means 10 of detecting temperature in the container; second temperature detection means 11 of detecting temperature of the pedestal; control means 14 of controlling the heating means and cooling means on the basis of detection results of the first temperature detection means and second temperature detection means; imaging means 12 of imaging a state of the sample heated by the heating means; and image analysis means 14 of determining the contact angle on the basis of an image picked up by the imaging means.