A lock device equipped with an opening support mechanism, the device comprising: an operation mechanism mountable to a stile of a sliding door and configured to be operated with an operation handle; the opening support mechanism configured to kick out the sliding door; a link bar configured to connect between the operation mechanism and the opening support mechanism; and a lock configured to unlock or lock the sliding door in conjunction with turning of the operation handle, wherein the operation mechanism includes a slider configured to move vertically in conjunction with the turning of the operation handle, the opening support mechanism includes: a guide pin attachment unit connected to the link bar at a predetermined interval from the slider, the link bar being connected to the slider and transmitting a vertical motion of the slider; a kick-out arm configured to turn in order to press one of a sliding door jamb and a vertical frame in conjunction with the vertical motion of the guide pin attachment unit; and an operation delay unit configured to delay a kick-out operation by the kick-out arm in order for the kick-out operation by the kick-out arm in the opening support mechanism to be performed after the sliding door is unlocked by the lock, characterized in that the lock device further comprises an idle lock prevention mechanism including a door stop portion, wherein the idle lock prevention mechanism is mountable to the stile of the sliding door while being biased in a direction at which the door stop portion protrudes from the stile, the idle lock prevention mechanism is configured to: be engaged with the link bar to inhibit the vertical motion of the link bar when the sliding door is positioned away from a frame body (1a,1b,1c) at a predetermined distance; and configured to be brought into contact with one of the sliding door jamb and the vertical frame to be disengaged from the link bar to allow both of the vertical motion of the link bar and the turning of the operation handle when the sliding door is positioned within the predetermined distance from the frame body (1a,1b,1c), wherein the door stop portion includes a groove with a width which corresponds to the predetermined distance. an operation mechanism mountable to a stile of a sliding door and configured to be operated with an operation handle; the opening support mechanism configured to kick out the sliding door; a link bar configured to connect between the operation mechanism and the opening support mechanism; and a lock configured to unlock or lock the sliding door in conjunction with turning of the operation handle, wherein the operation mechanism includes a slider configured to move vertically in conjunction with the turning of the operation handle, the opening support mechanism includes: a guide pin attachment unit connected to the link bar at a predetermined interval from the slider, the link bar being connected to the slider and transmitting a vertical motion of the slider; a kick-out arm configured to turn in order to press one of a sliding door jamb and a vertical frame in conjunction with the vertical motion of the guide pin attachment unit; and an operation delay unit configured to delay a kick-out operation by the kick-out arm in order for the kick-out operation by the kick-out arm in the opening support mechanism to be performed after the sliding door is unlocked by the lock, characterized in that a guide pin attachment unit connected to the link bar at a predetermined interval from the slider, the link bar being connected to the slider and transmitting a vertical motion of the slider; a kick-out arm configured to turn in order to press one of a sliding door jamb and a vertical frame in conjunction with the vertical motion of the guide pin attachment unit; and an operation delay unit configured to delay a kick-out operation by the kick-out arm in order for the kick-out operation by the kick-out arm in the opening support mechanism to be performed after the sliding door is unlocked by the lock, characterized in that the lock device further comprises an idle lock prevention mechanism including a door stop portion, wherein the idle lock prevention mechanism is mountable to the stile of the sliding door while being biased in a direction at which the door stop portion protrudes from the stile, the idle lock prevention mechanism is configured to: be engaged with the link bar to inhibit the vertical motion of the link bar when the sliding door is positioned away from a frame body (1a,1b,1c) at a predetermined distance; and configured to be brought into contact with one of the sliding door jamb and the vertical frame to be disengaged from the link bar to allow both of the vertical motion of the link bar and the turning of the operation handle when the sliding door is positioned within the predetermined distance from the frame body (1a,1b,1c), wherein the door stop portion includes a groove with a width which corresponds to the predetermined distance. be engaged with the link bar to inhibit the vertical motion of the link bar when the sliding door is positioned away from a frame body (1a,1b,1c) at a predetermined distance; and configured to be brought into contact with one of the sliding door jamb and the vertical frame to be disengaged from the link bar to allow both of the vertical motion of the link bar and the turning of the operation handle when the sliding door is positioned within the predetermined distance from the frame body (1a,1b,1c), wherein the door stop portion includes a groove with a width which corresponds to the predetermined distance.