The invention provides a frequency-modulated continuous-wave radar device and an object detecting method using continuous waves thereof. The frequency-modulated continuous-wave (FMCW) radar device comprises a continous wave (CW) signal generator configured to generate and transmit (Tx) CW signals, a radio frequency (RF) transmitter configured to send generated Tx CW signals as radio frequency signals through a Tx antenna, an RF receiver configured to receive reflected CW signals reflected and returned from a front object after the Tx CW signals are transmitted, a target detector configured to extract speed and angle by using the frequency difference between the Tx CW signals and the reflected CW signals and detect an approaching target, and a detection controller configured to control the predetermined time of the RF transmitter transmitting the Tx CW signals as signals having triangular wave forms in a time frequency graph and additionally transmitting the Tx CW signal as signals with cross strip wave forms with predetermined frequency.