A quadrature radar apparatus includes a quadrature signal generating unit, a plurality of coupler modules connected to the signal generating unit, an antenna unit receiving transmission signals from the coupler modules and a reception signal reflected from a target, one or more phase delay modules connected between one or more of the coupler modules and the antenna unit to delay the phases of the transmission and reception signals by 90 degrees, a leakage signal canceling unit combining the reception signals inputted from the antenna unit through the first and second coupler modules and removes the transmission leakage signal.