A machining fluid temperature deviation alarm device is attached to an electrical discharge machining device which, having a temperature sensor (S1) for machining fluid temperature detection and a cooler (2) for machining fluid cooling, controls the cooler in response to a temperature sensor output signal, thereby controlling the machining fluid temperature within an allowable range. The alarm device employs a second temperature sensor (S2) for determining whether the machining fluid temperature is within a predetermined temperature range set by means of a second setter (5) and encompassing the allowable machining fluid temperature range. In response to an output signal from the second temperature sensor, indicative of a deviation of the machining fluid temperature from the predetermined temperature range, a numerical control device (3) causes a CRT display unit (6) to display a temperature deviation message, and stops the operation of the electrical discharge machining device, thereby preventing lowering of machining accuracy, fluctuation of machining speed, and unstable electrical discharge machining that are attributable to the deviation of the machining fluid temperature.