A method for dividing a prediction block, an encoding device, and a decoding device, is disclosed. The method includes: acquiring a manner of division into the prediction block, where the manner of division into the prediction block is a horizontal division manner, a vertical division manner, or a square division manner, determining a horizontal division size and a vertical division size according to the manner of division into the prediction block, and dividing the prediction block into at least one prediction subblock according to the horizontal division size and the vertical division size.