A state determining method for determining at least a breakage state of a machine, the state determining method comprising: a light emission step of causing white light emitted by a light-emitting element (1, 72) to pass through oil (9, 40a) of the machine; a light receiving step of causing a light-receiving element (2, 73) to detect a color of the light that has passed through the oil (9, 40a) according to the light emission step; a brightness calculation step of calculating brightness of the color detected according to the light receiving step; a color component calculation value calculating step of calculating a color component calculation value that is a value calculated based on a maximum value and a minimum value among an R value, a G value, and a B value of the color detected according to the light receiving step; and a state determination step of determining the state based on the brightness calculated according to the brightness calculation step and the color component calculation value calculated according to the color component calculation value calculating step, wherein the state determination step includes a machine breakage state determining step of determining the breakage state of the machine, the color component calculation value is a difference between the maximum value and the minimum value, and the machine breakage state determining step is a step of determining the breakage state of the machine in accordance with an amount of decrease in the color component calculation value in comparison with that at a point of time when both the brightness calculated according to the brightness calculation step and the color component calculation value calculated according to the color component calculation value calculating step start to decrease. a light emission step of causing white light emitted by a light-emitting element (1, 72) to pass through oil (9, 40a) of the machine; a light receiving step of causing a light-receiving element (2, 73) to detect a color of the light that has passed through the oil (9, 40a) according to the light emission step; a brightness calculation step of calculating brightness of the color detected according to the light receiving step; a color component calculation value calculating step of calculating a color component calculation value that is a value calculated based on a maximum value and a minimum value among an R value, a G value, and a B value of the color detected according to the light receiving step; and a state determination step of determining the state based on the brightness calculated according to the brightness calculation step and the color component calculation value calculated according to the color component calculation value calculating step, wherein the state determination step includes a machine breakage state determining step of determining the breakage state of the machine, the color component calculation value is a difference between the maximum value and the minimum value, and the machine breakage state determining step is a step of determining the breakage state of the machine in accordance with an amount of decrease in the color component calculation value in comparison with that at a point of time when both the brightness calculated according to the brightness calculation step and the color component calculation value calculated according to the color component calculation value calculating step start to decrease.