A time-to-digital converting circuit and a pressure sensing device using the same are provided. The circuit includes: a delay time-varying unit generating a reference signal having a fixed delay time, and a sensing signal having a variable delay time in response to an impedance of an externally applied signal; and a delay time calculation and data generation unit calculating a delay time difference between the reference signal and the sensing signal, and generating digital data having a value corresponding to the calculated delay time difference. Accordingly, the digital data are generated using the delay time varied in response to the externally applied signal, so that the size of the time-to-digital circuit is significantly reduced. In addition, an affect due to external noises is minimized.