To provide a guide support device of a temporarily installed elevator for pit which can be safely extended and removed by less work man-hour and in a short work time and has a simple structure.

A guide support device of a temporarily installed elevator consists of a guide and support means which is fixed on a side face 1 of a pit and guides and supports a guide support 3 so as to lift it freely and bind the movement in the horizontal direction, the guide support 3 which is guided by the guide and support means and is elongated in the vertical direction, and a hoisting down support means H (a support rod and a support rod receive means 6) which is engaged with a predetermined supported part (through hole) of the guide support 3 at a position above an upper end of the pit and hoists down and supports the guide support 3. The guide support 3 is constituted by vertically connecting guide support unit bodies which are provided with the supported part (through hole) in the vicinity of at least an upper end and have a predetermined length, and the connection and disconnection of the guide support unit bodies are done at, for example, a work stage or the like which constitutes a part of the hoisting down support means H positioned above the upper end of the pit.