A temperature sensing unit comprising: an input portion to which at least a resistance temperature detector and a thermocouple can be selectively connected as a temperature sensor for sensing a temperature of a controlled object; a processing portion (21, 22), performing a temperature sensing processing of processing a sensing signal of the temperature sensor connected to the input portion and acquiring the temperature of the controlled object; and a temperature sensor type setting portion, setting a type of a temperature sensor to be connected to the input portion, and wherein the input portion comprises a first connection terminal to which one end of a temperature sensing resistance countermeasure element of the resistance temperature detector is connected, a second connection terminal to which the other end of the temperature sensing resistance countermeasure element of the resistance temperature detector or one end of the thermocouple is selectively connected, and a third connection terminal to which the other end of the thermocouple is connected, the temperature sensing unit being characterized in that when the type of the temperature sensor set by the temperature sensor type setting portion is a thermocouple, the processing portion (21, 22) performs an erroneous connection detecting processing of detecting whether or not the temperature sensor connected to the input portion is a thermocouple by determining that the connection is erroneous if an inter-terminal voltage between the first connection terminal and the second connection terminal is equal to or smaller than a threshold voltage set in advance in a state in which a constant current flows through the first connection terminal and the second connection terminal, wherein the threshold voltage is a value which is smaller than a voltage between the first connection terminal and the second connection terminal when the thermocouple is connected to the input portion and is greater than a maximum voltage between the first connection terminal and the second connection terminal when the resistance temperature detector is connected to the input portion. an input portion to which at least a resistance temperature detector and a thermocouple can be selectively connected as a temperature sensor for sensing a temperature of a controlled object; a processing portion (21, 22), performing a temperature sensing processing of processing a sensing signal of the temperature sensor connected to the input portion and acquiring the temperature of the controlled object; and a temperature sensor type setting portion, setting a type of a temperature sensor to be connected to the input portion, and wherein the input portion comprises a first connection terminal to which one end of a temperature sensing resistance countermeasure element of the resistance temperature detector is connected, a second connection terminal to which the other end of the temperature sensing resistance countermeasure element of the resistance temperature detector or one end of the thermocouple is selectively connected, and a third connection terminal to which the other end of the thermocouple is connected, the temperature sensing unit being characterized in that when the type of the temperature sensor set by the temperature sensor type setting portion is a thermocouple, the processing portion (21, 22) performs an erroneous connection detecting processing of detecting whether or not the temperature sensor connected to the input portion is a thermocouple by determining that the connection is erroneous if an inter-terminal voltage between the first connection terminal and the second connection terminal is equal to or smaller than a threshold voltage set in advance in a state in which a constant current flows through the first connection terminal and the second connection terminal, wherein the threshold voltage is a value which is smaller than a voltage between the first connection terminal and the second connection terminal when the thermocouple is connected to the input portion and is greater than a maximum voltage between the first connection terminal and the second connection terminal when the resistance temperature detector is connected to the input portion.