A dynamic-image displaying workstation provided with a display device for displaying an image, a video signal processing circuit for outputting dynamic-image data representing a dynamic image corresponding to a video signal, a first dual port memory for receiving and storing the dynamic-image data outputted from the video signal processing circuit, a second dual port memory for storing data representing pixels of an image to be displayed by the display device, and a third dual port memory for storing data representing a window area. The window area is an area of a window, to which the dynamic-image belongs, and is not covered by any other windows. The workstation is further provided with a fourth dual port memory for storing data representing a dynamic-image display effective area corresponding to the dynamic image represented by the dynamic-image stored in the first dual port memory, a data selector for receiving data read from the first dual port memory at a first input terminal thereof, and data read from the second dual port memory at a second input terminal thereof, for selecting one of the third and fourth dual port memories and receiving data read from the selected dual port memory at a third input terminal thereof, for selecting the data received at the first input terminal thereof if the data read from the third dual port memory is the data representing the window area, and the data read from the third dual port memory is the data representing the dynamic-image display effective area, for selecting the data received at the second input terminal thereof and for outputting a signal representing the selected data to the display device.