A lifter rotation preventing structure including: a lifter body (20, 20A) inserted into a sliding hole (93, 93A) of a housing (91, 91A) and reciprocated according to rotation of a cam (94, 94A), the lifter body (20, 20A) having a peripheral wall (21, 21A) slidable in the sliding hole (93, 93A) and a partition wall (23, 23A) partitioning an inside of the peripheral wall (21, 21A) into a first space (24, 24A) in which the cam (94, 94A) is located and a second space (25, 25A) located opposite the first space; a retainer (60, 60A) disposed in the second space (25, 25A) of the lifter body (20, 20A) and having a retainer body (61, 61A) located inside the peripheral wall (21, 21A) and connected to an engaging member (80, 81) reciprocally displaced together with the lifter body (20, 20A); and a biasing member (85, 85A) disposed in the second space (25, 25A) of the lifter body (20, 20A) and interposed between the retainer body (61, 61A) and the housing (91, 91A) to bias the lifter body (20, 20A) to the cam (94, 94A) side, characterized in that: the retainer (60, 60A) has a rotation preventing protrusion (63, 63A) protruding from an outer periphery of the retainer body (61, 61A) and fittingly extending through the peripheral wall (21, 21A); and the rotation preventing protrusion (63, 63A) has a distal end (64, 64A) moved into a rotation preventing groove (96, 96A) communicating with the sliding hole (93, 93A) of the housing (91, 91A) thereby to prevent the lifter body (20, 20A) from rotation. a lifter body (20, 20A) inserted into a sliding hole (93, 93A) of a housing (91, 91A) and reciprocated according to rotation of a cam (94, 94A), the lifter body (20, 20A) having a peripheral wall (21, 21A) slidable in the sliding hole (93, 93A) and a partition wall (23, 23A) partitioning an inside of the peripheral wall (21, 21A) into a first space (24, 24A) in which the cam (94, 94A) is located and a second space (25, 25A) located opposite the first space; a retainer (60, 60A) disposed in the second space (25, 25A) of the lifter body (20, 20A) and having a retainer body (61, 61A) located inside the peripheral wall (21, 21A) and connected to an engaging member (80, 81) reciprocally displaced together with the lifter body (20, 20A); and a biasing member (85, 85A) disposed in the second space (25, 25A) of the lifter body (20, 20A) and interposed between the retainer body (61, 61A) and the housing (91, 91A) to bias the lifter body (20, 20A) to the cam (94, 94A) side, characterized in that: the retainer (60, 60A) has a rotation preventing protrusion (63, 63A) protruding from an outer periphery of the retainer body (61, 61A) and fittingly extending through the peripheral wall (21, 21A); and the rotation preventing protrusion (63, 63A) has a distal end (64, 64A) moved into a rotation preventing groove (96, 96A) communicating with the sliding hole (93, 93A) of the housing (91, 91A) thereby to prevent the lifter body (20, 20A) from rotation. the retainer (60, 60A) has a rotation preventing protrusion (63, 63A) protruding from an outer periphery of the retainer body (61, 61A) and fittingly extending through the peripheral wall (21, 21A); and the rotation preventing protrusion (63, 63A) has a distal end (64, 64A) moved into a rotation preventing groove (96, 96A) communicating with the sliding hole (93, 93A) of the housing (91, 91A) thereby to prevent the lifter body (20, 20A) from rotation.