A load detection means (180) that finds the live load on a work platform by detecting a load applied to a fifth mast member (150) is provided on the fifth mast member (150) provided on the work platform; a plurality of sliders (top-rear side fourth slider (155), bottom-rear side fourth slider (156), top-front side fourth slider (157), and bottom-front side fourth slider (158)) that allows the fifth mast member (150) and the fourth mast member to move relative to each other is provided in different locations in the vertical direction between the fifth mast member (150) and the fourth mast member; and the plurality of sliders are fixed to the fifth mast member (150).