A sliding gate device includes a fixed plate fixed to a molten steel container, a sliding plate for opening/closing a nozzle hole, a sliding device moving a case holding the sliding plate, and a contact pressure control mechanism switching between a contact pressure applied state and a no-contact-pressure applied state for the fixed plate and the sliding plate. The contact pressure control mechanism has a support bar member moving relative to the fixed plate, a joining block tool switching between a joined state where the support bar member and the case cooperate with each other, and a joining-released state where the support bar member and the case do not cooperate with each other, and a spring member generating a force applying a contact pressure according to a position of the support bar member.