A radar device is disclosed. The radar device includes a radar antenna, from which detection signals are transmitted while the radar antenna being rotated, the radar device generating a radar image from reflection waves of the transmitted detection signals, a reception module for receiving the reflection waves of the detection signals, an inclination calculating module for calculating an inclination of level of the received signals that continue in a predetermined direction, the inclination being a rate of change in the received signal level per predetermined range in the predetermined direction, and a rain/snow reflection determining module for determining whether the received signals are reflection signals from at least one of rain and snow by using the inclination calculated by the inclination calculating module.