The invention discloses a phased-array ultrasonic detection device for the inner-hole defects of hole parts. The phased-array ultrasonic detection device comprises a probe positioning device, a phased-array ultrasonic probe (7), a signal processing device, a detection container (8) and a bench (9), wherein the detection container (8) and the probe positioning device are both mounted on the bench (9); and the probe positioning device comprises a longitudinal slide block (1), a transverse slide block (2), a longitudinal slide rail (3), a transverse slide rail (4), a transmission rod (5) and a probe clamp (6). The phased-array ultrasonic detection device has the advantage that a workpiece can be detected by means of water immersion, the problem of reduction of acoustic wave strength caused by poor coupling of a coupling agent between the probe head and the workpiece can be avoided, the stability of a system is improved, the influence caused by human factors can be alleviated and a new solution is provided for detecting special-shaped hole parts of which the detection positions are hard to determine, such as gears, impellers, engine cylinder blocks.