A gear machining condition setting device receives a feeding amount determining parameter and a cutting speed determining parameter. A storage unit stores a cutting-in amount calculation formula representing a relation between a cutting-in amount and a characteristic value determined based on a feeding amount and the feeding amount determining parameter. The feeding amount of the hob, corresponding to the cutting-in amount, is computed using the cutting-in amount calculation formula. Further, the storage unit stores data of a constant temperature curve representing a relation between the cutting-in amount and the cutting speed where a cutting edge of the hob is set at a predetermined temperature. Using the data, the cutting speed is computed based on the cutting-in amount and the cutting speed determining parameter with reference to the constant temperature curve.