The invention discloses an automatic temperature control device, which comprises a temperature detection circuit and a temperature control circuit, wherein the temperature detection circuit is composed of a temperature sensor RT, three-terminal precise voltage regulators IC1 and IC2, potentiometers RP1, RP2, and RP5, an ammeter PA, resistors R3 to R6 and a temperature measurement setting selection switch S; and the temperature control circuit is composed of three-terminal precise voltage regulators IC3 and IC4, a transistor V, a thyristor VT, zener diodes VS1 and VS2, a relay K, a diode VD, light-emitting diodes VL1 and VL2, resistors R1, R2, R7 to R10, a temperature upper limit control potentiometer RP3 and a temperature lower limit control potentiometer RP4. The temperature control device of the invention is wide in temperature control range, accurate in control, low in energy consumption and low in manufacturing cost, an electric heater is automatically closed when the monitored temperature reaches the upper set temperature limit value, and when the monitored temperature reaches the lower set temperature limit value, the working power supply of the electric heater is automatically connected.