An injection apparatus that performs a low speed operation, a high speed operation, and a pressurizing operation to inject and fill a molding material into a mold, the injection apparatus comprising: a high speed operation cylinder operated during the high speed operation and including a rod (40c, 40f) and an operation chamber (40d, 40e); an accumulating unit connected to the operation chamber (40d, 40e) to supply operational pressure to the operation chamber (40d, 40e) and move the rod (40c, 40f); and a connection mechanism switchable between a connected state, in which the connection mechanism restricts movement of the rod (40c, 40f) caused by the operational pressure of the accumulating unit, and a disconnected state, in which the connection mechanism cancels the connected state so that the rod (40c, 40f) is movable by the operational pressure, characterized in that the connection mechanism includes a first connection member, a second connection member, and a drive source, wherein the first connection member is rotatably supported by the rod (40c, 40f) and includes a first abutment surface and a first rotation axis extending in a direction substantially orthogonal to an axis of the rod (40c, 40f), the second connection member includes a second abutment surface that comes into planar contact with the first abutment surface to form a joined surface with the first abutment surface, the drive source rotates the second connection member about a second rotation axis, a hypothetical axis is defined by an axis lying on and orthogonal to the axis of the rod (40c, 40f) and parallel to the first rotation axis, and a hypothetical plane is defined by a plane set by the axis of the rod (40c, 40f) and the hypothetical axis, a referential connection state is defined by a situation in which at least a portion of the joined surface extends at a right angle relative to the hypothetical plane, a normal direction extending toward the second connection member in the first abutment surface conforms with a direction in which the rod (40c, 40f) is moved by the operational pressure of the accumulating unit, and the first rotation axis substantially conforms to the second rotation axis, the connection mechanism remains in the connected state until the second connection member is rotated by the drive source from the referential connection state by less than 90 degrees in either one of a forward direction and a reverse direction, and when the second connection member is rotated by the drive source in the connected state, the first connection member is rotated with the first abutment surface in planar contact with the second abutment surface. a high speed operation cylinder operated during the high speed operation and including a rod (40c, 40f) and an operation chamber (40d, 40e); an accumulating unit connected to the operation chamber (40d, 40e) to supply operational pressure to the operation chamber (40d, 40e) and move the rod (40c, 40f); and a connection mechanism switchable between a connected state, in which the connection mechanism restricts movement of the rod (40c, 40f) caused by the operational pressure of the accumulating unit, and a disconnected state, in which the connection mechanism cancels the connected state so that the rod (40c, 40f) is movable by the operational pressure, characterized in that the connection mechanism includes a first connection member, a second connection member, and a drive source, wherein the first connection member is rotatably supported by the rod (40c, 40f) and includes a first abutment surface and a first rotation axis extending in a direction substantially orthogonal to an axis of the rod (40c, 40f), the second connection member includes a second abutment surface that comes into planar contact with the first abutment surface to form a joined surface with the first abutment surface, the drive source rotates the second connection member about a second rotation axis, a hypothetical axis is defined by an axis lying on and orthogonal to the axis of the rod (40c, 40f) and parallel to the first rotation axis, and a hypothetical plane is defined by a plane set by the axis of the rod (40c, 40f) and the hypothetical axis, a referential connection state is defined by a situation in which at least a portion of the joined surface extends at a right angle relative to the hypothetical plane, a normal direction extending toward the second connection member in the first abutment surface conforms with a direction in which the rod (40c, 40f) is moved by the operational pressure of the accumulating unit, and the first rotation axis substantially conforms to the second rotation axis, the connection mechanism remains in the connected state until the second connection member is rotated by the drive source from the referential connection state by less than 90 degrees in either one of a forward direction and a reverse direction, and when the second connection member is rotated by the drive source in the connected state, the first connection member is rotated with the first abutment surface in planar contact with the second abutment surface.