To provide a device capable of simultaneously attaining high efficiency and high control performance, in the hydraulic drive unit using a hydraulic cylinder.

A separate oil hydraulic pump 21, 22 is connected respectively to an extending/contacting side oil chamber 11, 12 of a hydraulic cylinder 10, these pumps are driven by a separate electric servomotor 31, 32. In a control means 1, a command relating to the electric servomotor 31, 32 is respectively calculated, based on displacement and its target value of the hydraulic cylinder 10 detected by a displacement detector 14. In this way, by independently controlling the respective oil hydraulic motors 21, 22, this constitution, though generating no loss flow amount, can prevent generation of a negative pressure in the hydraulic cylinder 10 with no use of a check valve or the like.