A retaining unit (1, 2, 3, 4, 5, 6) which is used in a state being incorporated in an ejection mechanism (140, 240) of a molding die assembly (100, 200, 400, 410), the molding die assembly (100, 200, 400, 410) provided for molding a molded article by a fixed-side die and a movable-side die, the ejection mechanism (140, 240) of the molding die assembly (100, 200, 400, 410) comprising an ejector plate (141, 241), the retaining unit (1, 2, 3, 4, 5, 6) comprising: a first member (10, 40, 50, 60, 73) configured to be movable and which functions as an ejector pin; a second member (11, 81) used in an unmovable fixed state which is fixed to the ejector plate; and a pressing element attached to the second member (11, 81), and configured to press the first member (10, 40, 50, 60, 73) to engage the first member (10, 40, 50, 60, 73) with the second member (11, 81), wherein the retaining unit (1, 2, 3, 4, 5, 6) is configured such that the first member (10, 40, 50, 60, 73) can be moved by release of the engagement with the second member when a force at a predetermined level or higher is applied in a movement direction of the first member (10, 40, 50, 60, 73), and the pressing element is assembled with the second member to constitute a unit, wherein the first member (10, 40, 50, 60, 73) has a body portion, a distal end portion of the first member that has a smaller width than the body portion, and an enlarged portion (22, 82) that is disposed at a proximal end of the body portion and has a larger width than the body portion, the pressing element is incorporated so as to press the enlarged portion (22, 82), the stroke amount of the ejector pin is restricted by a step portion between the body portion and the distal end portion of the ejector pin, and the second member (11, 81) is a ring-shaped member provided so as to surround a pressed portion of the first member (10, 40, 50, 60, 73). a first member (10, 40, 50, 60, 73) configured to be movable and which functions as an ejector pin; a second member (11, 81) used in an unmovable fixed state which is fixed to the ejector plate; and a pressing element attached to the second member (11, 81), and configured to press the first member (10, 40, 50, 60, 73) to engage the first member (10, 40, 50, 60, 73) with the second member (11, 81), wherein the retaining unit (1, 2, 3, 4, 5, 6) is configured such that the first member (10, 40, 50, 60, 73) can be moved by release of the engagement with the second member when a force at a predetermined level or higher is applied in a movement direction of the first member (10, 40, 50, 60, 73), and the pressing element is assembled with the second member to constitute a unit, wherein the first member (10, 40, 50, 60, 73) has a body portion, a distal end portion of the first member that has a smaller width than the body portion, and an enlarged portion (22, 82) that is disposed at a proximal end of the body portion and has a larger width than the body portion, the pressing element is incorporated so as to press the enlarged portion (22, 82), the stroke amount of the ejector pin is restricted by a step portion between the body portion and the distal end portion of the ejector pin, and the second member (11, 81) is a ring-shaped member provided so as to surround a pressed portion of the first member (10, 40, 50, 60, 73). the stroke amount of the ejector pin is restricted by a step portion between the body portion and the distal end portion of the ejector pin, and the second member (11, 81) is a ring-shaped member provided so as to surround a pressed portion of the first member (10, 40, 50, 60, 73).