A chemical liquid thermostat control device is provided, and has a chemical tank for accommodating a chemical liquid, PTC resistor patterns for heating and maintaining the chemical liquid in a constant temperature, a current limit circuit for controlling the PTC resistor patterns to heat or to stop heating according to a real-time resistance value of each of the PTC resistor patterns, so as to maintain the chemical liquid at the constant temperature. The PTC resistor patterns are uniformly spaced in the chemical tank and immersed in the chemical liquid. Each of the PTC resistor patterns is connected with the current limit circuit through a wire. A heating power of a heating device can be real-time adjusted for intelligently heating. Thus, it is safer and a fire risk can be prevented. The life time of the PTC resistor patterns is more than a decade, and doesn't need be replaced frequently.