A coolant supply device, comprising: a coolant tank including a first coolant reservoir, a second coolant reservoir, and a communicating part and formed to have a substantially U-shaped overall shape in plan view, the first and second coolant reservoirs (5, 7) each having a substantially rectangular shape in plan view and being arranged in parallel with a predetermined space therebetween, the communicating part being arranged at an end between the first and second coolant reservoirs (5, 7) and having one end connected to a sidewall of the first coolant reservoir and another end connected to a sidewall of the second coolant reservoir to allow the first coolant reservoir and the second coolant reservoir to communicate with each other; and a supply pump (30, 31, 32) pumping up coolant from the second coolant reservoir and supplying the coolant to a predetermined destination, the coolant supply device being configured such that the coolant supplied to the predetermined destination by the supply pump (30, 31, 32) is returned to the first coolant reservoir and coolant in the first coolant reservoir flows into the second coolant reservoir through the communicating part, characterized in that: the coolant supply device is configured to include: at least one agitation pump pumping up coolant from the coolant tank; a first agitating nozzle body disposed in the first coolant reservoir and discharging the coolant supplied by the agitation pump to assist a flow of coolant flowing toward the communicating part; and a second agitating nozzle body disposed in the second coolant reservoir and discharging the coolant supplied by the agitation pump to assist a flow of coolant flowing into the second coolant reservoir from the communicating part. a coolant tank including a first coolant reservoir, a second coolant reservoir, and a communicating part and formed to have a substantially U-shaped overall shape in plan view, the first and second coolant reservoirs (5, 7) each having a substantially rectangular shape in plan view and being arranged in parallel with a predetermined space therebetween, the communicating part being arranged at an end between the first and second coolant reservoirs (5, 7) and having one end connected to a sidewall of the first coolant reservoir and another end connected to a sidewall of the second coolant reservoir to allow the first coolant reservoir and the second coolant reservoir to communicate with each other; and a supply pump (30, 31, 32) pumping up coolant from the second coolant reservoir and supplying the coolant to a predetermined destination, the coolant supply device being configured such that the coolant supplied to the predetermined destination by the supply pump (30, 31, 32) is returned to the first coolant reservoir and coolant in the first coolant reservoir flows into the second coolant reservoir through the communicating part, characterized in that: the coolant supply device is configured to include: at least one agitation pump pumping up coolant from the coolant tank; a first agitating nozzle body disposed in the first coolant reservoir and discharging the coolant supplied by the agitation pump to assist a flow of coolant flowing toward the communicating part; and a second agitating nozzle body disposed in the second coolant reservoir and discharging the coolant supplied by the agitation pump to assist a flow of coolant flowing into the second coolant reservoir from the communicating part. at least one agitation pump pumping up coolant from the coolant tank; a first agitating nozzle body disposed in the first coolant reservoir and discharging the coolant supplied by the agitation pump to assist a flow of coolant flowing toward the communicating part; and a second agitating nozzle body disposed in the second coolant reservoir and discharging the coolant supplied by the agitation pump to assist a flow of coolant flowing into the second coolant reservoir from the communicating part.