A method and arrangement for automatic elevator installation includes marking each door opening in the elevator shaft with door reflectors, and creating a reference coordinate system of the elevator shaft with a robotic total station positioned at a bottom of the elevator shaft, measuring the position of the door reflectors with the robotic total station, fitting straight door lines to the measurements in order to form virtual plumb lines for the doors in the elevator shaft, marking predetermined guide rail positions on the bottom of the elevator shaft and installing lowermost guide rails manually to the shaft based on the guide rail positions, forming vertical guide rail lines, i.e. virtual plumb lines for the guide rails with the robotic total station based on the door lines, providing an upwards and downwards movable installation platform in the elevator shaft provided with platform reflectors, and measuring the position of the platform reflectors with the robotic total station, whereby the orientation and the position of the installation platform in relation to the elevator shaft can be determined.