The invention relates to a frozen-seafood sampling device for a laboratory. The problems that in the process of detecting microorganisms of frozen seafood, sampling difficulty is high, and time and labor are wasted are solved. The device comprises a handheld part, a sampling cylinder and a stretchable electric cylinder. The sampling cylinder is cylindrical, the back end of the sampling cylinder is rotationally connected to the handheld part in an inserted mode, and a cutting head is arranged on the front end face of the sampling cylinder. A motor is arranged in the handheld part and connected with the sampling cylinder and the stretchable electric cylinder through a planetary gear mechanism, an output shaft of the motor is connected with a sun gear of the planetary gear mechanism, a planetary carrier of the planetary gear mechanism is connected with the stretchable electric cylinder, and a rack of the planetary gear mechanism is connected with the sampling cylinder and connected with the handheld part through a ratchet wheel which can rotate in the forward direction and is locked in the backward direction. The stretchable electric cylinder comprises a cylinder body and a piston. When the motor carries out forward-direction outputting, the ratchet wheel can rotate in the forward direction for outputting, and the piston of the stretchable electric cylinder is retracted; when the motor carries out backward-direction outputting, the ratchet wheel is locked, and the piston of the stretchable electric cylinder is stretched. By means of the frozen-seafood sampling device, convenience is brought to sampling of frozen seafood in the laboratory, and sampling efficiency is improved.