A temperature sensing device includes a first frequency generator for generating a first clock signal having a first frequency that is constant regardless of a temperature; a second frequency generator for generating a second clock signal having a second frequency that is changed according to the temperature; and a data holding unit for outputting a temperature code indicating a number of pulses of the second clock signal counted for a reference time at which a number of pulses of the first clock signal reaches a predetermined threshold. The temperature sensing device does not require a reference clock signal input from the outside and is insensitive to the change in the process, thereby being capable of improving the performance of the temperature sensing device.