An electrically-driven flow rate control valve comprising: a casing including a first fluid chamber, a second fluid chamber, a fluid-chamber communication port for causing the first fluid chamber and the second fluid chamber to communicate with each other, and a cylinder portion, wherein a reception port capable of receiving a fluid from an outside of the casing into the first fluid chamber and a discharge port capable of discharging the fluid from the second fluid chamber to the outside of the casing are formed on the casing; an electric motor; a main valve body, which is stored in the cylinder portion so as to be movable between a main-valve-body open position and a main-valve-body sealing position along a predetermined axial direction, forms a back pressure chamber which the fluid can enter into/exit from between the main valve body and the cylinder portion, and includes a main-valve-body distal end portion capable of sealing the fluid-chamber communication port and a main-valve-body base end portion facing the back pressure chamber on an opposite side of the main-valve-body distal end portion in the axial direction, wherein the main-valve-body distal end portion opens the fluid-chamber communication port, thereby permitting communication of the fluid between the first fluid chamber and the second fluid chamber when the main valve body is arranged at the main-valve-body open position, and the main-valve-body distal end portion seals the fluid-chamber communication port, thereby shutting off the communication of the fluid between the first fluid chamber and the second fluid chamber when the main valve body is arranged at the main-valve-body sealing position; a communication path capable of causing the first fluid chamber and the back pressure chamber to communicate with each other; a flow-rate regulating mechanism, which is arranged in the communication path, and regulates a flow rate of the fluid so as to reduce the flow rate of the fluid flowing from the first fluid chamber toward the back pressure chamber; and a sub valve body, which is stored in the back pressure chamber, includes a sub-valve-body flow path communicating with the outside of the casing and a sub-valve-body communication port causing the back pressure chamber and the sub-valve-body flow path to communicate with each other, receives a driving force generated by the electric motor, thereby being capable of relatively moving along the axial direction with respect to the main valve body between a sub-valve-body open position and a sub-valve-body sealing position, opens the sub-valve-body communication port, thereby permitting the fluid in the back pressure chamber to be discharged via the sub-valve-body flow path to the outside of the casing when the sub valve body is arranged at the sub-valve-body open position, and seals the sub-valve-body communication port, thereby shutting off the communication of the fluid between the back pressure chamber and the sub-valve-body flow path when the sub valve body is arranged at the sub-valve-body sealing position, wherein the main valve body has such a shape as satisfying a relationship of AS<AT where AS is an area of the main-valve-body distal end portion projected in the axial direction, and AT is an area of the main-valve-body base end portion projected in the axial direction.