A sliding assistance mechanism for assisting switchover operation in which a mobile body is switched from a first position on the body side to a second position or from the second position to the first position. The mechanism has a case (1) installed on the body side, a first motion member and second motion member (sliders (2A, 2B)) individually slidably arranged on the case (1), a pair of latches (5, 5) supported by the respective motion members and releasably engaged with corresponding portions on the case side, and urging means (3) placed between both motion members. When the mobile body is switched to a position in the middle from the second position to the first position or to a position in the middle from the first position to the second position, engagement of either of the latchesis released by an engagement pin (9) attached to the mobile body, and the engagement pin together with the latch is pulled in to the first position or the second position.During the pull-in operation, the pin is driven via the motion members and urging means (3) and made to approach the other latch side.