A light detection and ranging (LIDAR) device includes: a photodiode configured to generate a current in response to an optical signal being input to the photodiode; a current-voltage conversion circuit configured to convert the current into a voltage; an N-type ring voltage controlled oscillator (RVCO) configured to output a first pulse signal when the voltage is input to the N-type RVCO; a P-type RVCO configured to output a second pulse signal when the voltage is input to the P-type RVCO; and a processor configured to estimate an intensity of the optical signal by identifying, based on the first pulse signal and the second pulse signal, a digital signal value corresponding to the voltage.