An operation support apparatus for a heat-treatment furnace for heat-treating a metal plate continuously includes a required time calculation unit configured to calculate, based on a current furnace temperature which is a current temperature of the heat-treatment furnace, a current line speed which is a current conveyance speed of the metal plate, and a target line speed which is a conveyance speed of the metal plate to be changed from the current line speed, an estimated required time until a temperature of the heat-treatment furnace reaches, from the current furnace temperature, a target furnace temperature which is a temperature of the heat-treatment furnace corresponding to the target line speed, and a first output unit configured to output the estimated required time calculated by the required time calculation unit.