A power transmission system for a hybrid vehicle, the power transmission system comprising: an engine; a motor; a torque converter; a transmission; and a clutch, wherein the motor is connected to a driving wheel through the transmission, and the engine is connected to the motor through the clutch; the power transmission system further comprising: a first oil pump that supplies oil to the transmission; a second oil pump (68, 82, 92) that supplies oil to the motor and the clutch; the power transmission system characterized by a first case that houses the torque converter and the transmission, wherein an intermediate partition, which separates the torque converter and the transmission, is provided integrally with the first case and the first oil pump is provided in an inner peripheral part of the intermediate partition concentrically with a shaft center of the power transmission system; a second case that houses the second oil pump (68, 82, 92), the clutch and the motor; a first hydraulic circuit in which the first oil pump is provided, the first hydraulic circuit including a first valve body configured to switch an oil passage of the first hydraulic circuit and a first oil pan, the first valve body and the first oil pan being provided integrally with a lower end part of the first case; and a second hydraulic circuit in which the second oil pump (68, 82, 92) is provided, the second hydraulic circuit being independent from the first hydraulic circuit, the second hydraulic circuit including a second valve body configured to switch an oil passage of the second hydraulic circuit and a second oil pan, the second valve body and the second oil pan being provided integrally with a lower end part of the second case. an engine; a motor; a torque converter; a transmission; and a clutch, wherein the motor is connected to a driving wheel through the transmission, and the engine is connected to the motor through the clutch; the motor is connected to a driving wheel through the transmission, and the engine is connected to the motor through the clutch; the power transmission system further comprising: a first oil pump that supplies oil to the transmission; a second oil pump (68, 82, 92) that supplies oil to the motor and the clutch; a first oil pump that supplies oil to the transmission; a second oil pump (68, 82, 92) that supplies oil to the motor and the clutch; the power transmission system characterized by a first case that houses the torque converter and the transmission, wherein an intermediate partition, which separates the torque converter and the transmission, is provided integrally with the first case and the first oil pump is provided in an inner peripheral part of the intermediate partition concentrically with a shaft center of the power transmission system; a second case that houses the second oil pump (68, 82, 92), the clutch and the motor; a first hydraulic circuit in which the first oil pump is provided, the first hydraulic circuit including a first valve body configured to switch an oil passage of the first hydraulic circuit and a first oil pan, the first valve body and the first oil pan being provided integrally with a lower end part of the first case; and a second hydraulic circuit in which the second oil pump (68, 82, 92) is provided, the second hydraulic circuit being independent from the first hydraulic circuit, the second hydraulic circuit including a second valve body configured to switch an oil passage of the second hydraulic circuit and a second oil pan, the second valve body and the second oil pan being provided integrally with a lower end part of the second case.