Abstract: A hydraulic control system in a working machine includes hydraulic cylinders that make a working part ascend and descend; a first main pump that suctions oil from an oil tank and discharges the oil; an accumulator that accumulates oil discharged from weight holding side oil chambers of the hydraulic cylinders when the working part descends; and a hybrid pump that suctions accumulated oil pressure in the accumulator and discharges the oil pressure. When the working part ascends, discharged oil from the hybrid pump is supplied to the weight holding side oil chambers of the hydraulic cylinders. When an insufficient supply flow from the hybrid pump to the hydraulic cylinders exists, a complementary flow corresponding to the insufficient supply flow is supplied from the first main pump to the weight holding side oil chambers of the hydraulic cylinders.