An ultrasound diagnostic system includes a portable ultrasound diagnostic device and an extended docking device to which the portable ultrasound diagnostic device is detachably mounted, wherein at least one of probes and channels are extended when the portable ultrasound diagnostic device is mounted to the extended docking device. Also, the ultrasound diagnostic system may further include an indoor ultrasound diagnostic device including a portable docking part, and the portable ultrasound diagnostic device may include a cart-based docking part and be connected to the indoor ultrasound diagnostic device. The ultrasound diagnostic system may enhance portability of the portable ultrasound diagnostic device and simultaneously achieves superior ultrasound diagnostic performance and quality also in the portable ultrasound diagnostic device through extension of the probes, signal channels, diagnostic items, or diagnostic performance, as occasion demands.