A method for installing guide rails into an elevator shaft, said method comprising installing manually a lowermost first section of guide rail elements to respective walls of the shaft, arranging a first hoist for moving a transport apparatus upwards and downwards in the shaft, the transport apparatus comprising a hook device connected to the first hoist and a lever device connected to the hook device, each guide rail element being provided with a first jointing clamp attached to a lower end of the guide rail element and a second jointing clamp attached to an upper end of the guide rail element, the first jointing clamp and the second jointing clamp forming a plug-in joint between two consecutive guide rail elements, the lever device being movably supported with rollers or gliding shoes on the guide rail, arranging a second hoist for moving a transport platform upwards and downwards in the shaft, connecting a guide rail element to the transport apparatus so that the second jointing clamp at the upper end of the guide rail is connected to the hook device and the lower end of the guide rail element is connected to the lever device, moving the transport apparatus and thereby also the guide rail element upwards with the first hoist, the lever device moving on the row of already installed guide rail elements, connecting the guide rail element to an upper end of the row of already installed guide rail elements with the plug-in joint provided by the first jointing clamp and the second jointing clamp, attaching the guide rail element to a wall of the shaft from the transport platform, moving the transport apparatus downwards with the first hoist in order to fetch a new guide rail element, the hook device and the lever device moving on the row of already installed guide rail elements. installing manually a lowermost first section of guide rail elements to respective walls of the shaft, arranging a first hoist for moving a transport apparatus upwards and downwards in the shaft, the transport apparatus comprising a hook device connected to the first hoist and a lever device connected to the hook device, each guide rail element being provided with a first jointing clamp attached to a lower end of the guide rail element and a second jointing clamp attached to an upper end of the guide rail element, the first jointing clamp and the second jointing clamp forming a plug-in joint between two consecutive guide rail elements, the lever device being movably supported with rollers or gliding shoes on the guide rail, arranging a second hoist for moving a transport platform upwards and downwards in the shaft, connecting a guide rail element to the transport apparatus so that the second jointing clamp at the upper end of the guide rail is connected to the hook device and the lower end of the guide rail element is connected to the lever device, moving the transport apparatus and thereby also the guide rail element upwards with the first hoist, the lever device moving on the row of already installed guide rail elements, connecting the guide rail element to an upper end of the row of already installed guide rail elements with the plug-in joint provided by the first jointing clamp and the second jointing clamp, attaching the guide rail element to a wall of the shaft from the transport platform, moving the transport apparatus downwards with the first hoist in order to fetch a new guide rail element, the hook device and the lever device moving on the row of already installed guide rail elements.