To provide an apparatus and a method for quantitatively evaluating the combustion period of solid fuel under a prescribed use condition.

A sample 12 is burnt in a combustion chamber 14 under a prescribed condition, and the weight of the sample 12 is measured by a weight meter 3, after the start of combustion. The measured result of the weight meter 3 is transmitted to a data processing means 10. The data processing means 10 uses the preliminarily measured initial weight of the sample 12 and the measured result of the weight meter 3 to calculate a weight change ratio ΔW. The time required until the weight change ratio reaches a prescribed value is outputted as the combustion degree of solid fuel.