A coolant pump comprising a filter mechanism, wherein the filter is constituted of a filter element, a filter upper support member, and a filter lower support member, wherein the filter element is cylindrical and is accommodated in a first casing, a space is formed between the filter element and an inner wall surface of the first casing along a radial direction, a blade is arranged in the space formed along the radial direction, the blade extending to be parallel to a central axis of the first casing, and the blade being rotatable in that it is arranged to rotate in a circumferential direction of the filter element, wherein the pump has a pump drive electric motor arranged to drive the pump, wherein a radially inner region of the filter element communicates with an intake opening of the pump, whereby in use, a suction inlet pressure of the pump causes working fluid to flow from the outside toward the inside of the filter element, wherein in the space between the filter and the casing inner wall, when the rotating blade (61A, 61B, 61C, 61D) proceeds in the working fluid, a turbulent flow is generated behind the blade thereby generating a flow that sucks the working fluid from inside of the filter element to the outside of the filter element, whereby foreign matters are detached from the outer peripheral surface of the filter element by the turbulent flow or the flow that sucks the working fluid; and the coolant pump has a further pump unit, a filter casing lower end closing plate and a strainer plate, wherein the pump unit has an upper housing, a trochoid pump, and a lower housing, wherein a central space portion in the upper housing has a shape whose upper end side is opened and a coupling is arranged in the central space portion wherein coupling connects a rotary shaft of the pump drive electric motor to a pump shaft, wherein a first shaft through hole is formed at the centre of a filter upper support member and a lower end of the pump shaft and an upper end of a cylindrical rotary shaft penetrates through the first shaft through hole, and wherein an oil seal storage member is provided below the filter lower support member 53, and an oil seal is provided to the oil seal storage member and a second through hole is formed at the centre of the oil seal storage member and the cylindrical rotary shaft is rotatably pivoted in the second through hole, such that in use, when the cylindrical rotary shaft rotates, the rotary blade rotates and, in use, the rotation of the electric motor is transmitted to the rotary shaft, the pump shaft and to the cylindrical rotary shaft coupled with the pump shaft and the rotary blade and thereby the rotary blade rotates together with the trochoid pump. a space is formed between the filter element and an inner wall surface of the first casing along a radial direction, a blade is arranged in the space formed along the radial direction, the blade extending to be parallel to a central axis of the first casing, and the blade being rotatable in that it is arranged to rotate in a circumferential direction of the filter element, wherein the pump has a pump drive electric motor arranged to drive the pump, wherein a radially inner region of the filter element communicates with an intake opening of the pump, whereby in use, a suction inlet pressure of the pump causes working fluid to flow from the outside toward the inside of the filter element, wherein in the space between the filter and the casing inner wall, when the rotating blade (61A, 61B, 61C, 61D) proceeds in the working fluid, a turbulent flow is generated behind the blade thereby generating a flow that sucks the working fluid from inside of the filter element to the outside of the filter element, whereby foreign matters are detached from the outer peripheral surface of the filter element by the turbulent flow or the flow that sucks the working fluid; and the coolant pump has a further pump unit, a filter casing lower end closing plate and a strainer plate, wherein the pump unit has an upper housing, a trochoid pump, and a lower housing, wherein a central space portion in the upper housing has a shape whose upper end side is opened and a coupling is arranged in the central space portion wherein coupling connects a rotary shaft of the pump drive electric motor to a pump shaft, wherein a first shaft through hole is formed at the centre of a filter upper support member and a lower end of the pump shaft and an upper end of a cylindrical rotary shaft penetrates through the first shaft through hole, and wherein an oil seal storage member is provided below the filter lower support member 53, and an oil seal is provided to the oil seal storage member and a second through hole is formed at the centre of the oil seal storage member and the cylindrical rotary shaft is rotatably pivoted in the second through hole, such that in use, when the cylindrical rotary shaft rotates, the rotary blade rotates and, in use, the rotation of the electric motor is transmitted to the rotary shaft, the pump shaft and to the cylindrical rotary shaft coupled with the pump shaft and the rotary blade and thereby the rotary blade rotates together with the trochoid pump.