A steel plate manufacturing installation (1A) can switch a hot dip coating circuit (R1) for manufacturing hot dip coating steel plate (3a) and a cold rolling circuit (R2) for manufacturing cold rolling steel plate (3b). A switching furnace shell unit (10) for moving along horizontal direction is set on the hot dip coating circuit (R1) standing from hot dipping tauk (8) and the said switching furnace shell unit (10) is formed by a furnace shell (11) for the hot dip coating circuit at least being composed of alloying furnace (11a) and extending along vertical direction and a furnace shell (20) for cold rolling circuit extending along horizontal direction. On the hot dip coating circuit (R1), the switching furnace shell unit (10) is made to move towards one direction, and the furnace shell (11) for the hot dip coating circuit is same with the hot dip coating circuit (R1). When switching into the cold rolling circuit (R2), the switching furnace shell unit (10) moves towards the other direction. The cold rolling circuit is connected to the lower end of the furnace shell (20) for cold rolling circuit to bypass the hot dipping tauk (8) and the subsequent cold rolling circuit is connectedwith the upper end. The structure of the invention is simple and can switch the hot dip coating circuit and the cold rolling circuit.