A temperature control apparatus comprising: a plurality of temperature sensors configured to measure a plurality of temperature values of a target; an analog to digital, AD, converter configured to digital-convert the plurality of temperature values; a control means configured to compare the temperature values transmitted from the AD converter with a preset desired value to perform PID calculation; and an output unit which is configured to transmit, to the outside, a pulse width modulation, PWM, control signal transmitted from the control means, characterized in that: each input-side isolator among a plurality of input-side isolators is installed between the AD converter and a corresponding temperature sensor among the plurality of temperature sensors, each of the plurality of input-side isolators comprises: a pair of solid state relays (501, 502), each of the solid state relays comprising a light emitting diode and a phototransistor, the phototransistor being configured to start operations by light emitted from the light emitting diode, and the pair of solid state relays (501 and 502) comprising a first solid state relay and a second solid state relay, wherein an anode of the light emitting diode of the first solid state relay is mutually connected to a cathode of the light emitting diode of the second solid state relay, and wherein an anode of the light emitting diode of the second solid state relay is connected to a voltage source, wherein the phototransistor of the first solid state relay is connected to a plus terminal of the corresponding temperature sensor, and the phototransistor of the second solid state relay is connected to a minus terminal of the corresponding temperature sensor so that each of the plurality of temperature sensors is connected to a corresponding pair of solid state relays (501, 502), and the control means sequentially operates the plurality of input-side isolators. a plurality of temperature sensors configured to measure a plurality of temperature values of a target; an analog to digital, AD, converter configured to digital-convert the plurality of temperature values; a control means configured to compare the temperature values transmitted from the AD converter with a preset desired value to perform PID calculation; and an output unit which is configured to transmit, to the outside, a pulse width modulation, PWM, control signal transmitted from the control means, characterized in that: each input-side isolator among a plurality of input-side isolators is installed between the AD converter and a corresponding temperature sensor among the plurality of temperature sensors, each of the plurality of input-side isolators comprises: a pair of solid state relays (501, 502), each of the solid state relays comprising a light emitting diode and a phototransistor, the phototransistor being configured to start operations by light emitted from the light emitting diode, and the pair of solid state relays (501 and 502) comprising a first solid state relay and a second solid state relay, a pair of solid state relays (501, 502), each of the solid state relays comprising a light emitting diode and a phototransistor, the phototransistor being configured to start operations by light emitted from the light emitting diode, and the pair of solid state relays (501 and 502) comprising a first solid state relay and a second solid state relay, wherein an anode of the light emitting diode of the first solid state relay is mutually connected to a cathode of the light emitting diode of the second solid state relay, and wherein an anode of the light emitting diode of the second solid state relay is connected to a voltage source, wherein the phototransistor of the first solid state relay is connected to a plus terminal of the corresponding temperature sensor, and the phototransistor of the second solid state relay is connected to a minus terminal of the corresponding temperature sensor so that each of the plurality of temperature sensors is connected to a corresponding pair of solid state relays (501, 502), and the control means sequentially operates the plurality of input-side isolators.