The invention relates to a method for constructing an elevator comprising constructing a movable machine room in the bottom end of a hoistway formed in a building under construction; and thereafter hoisting the movable machine room; and constructing an elevator car in the bottom end of the hoistway below the movable machine room; and providing a counterweight in the bottom end of the hoistway below the movable machine room; connecting the elevator car and the counterweight with a suspension roping; and thereafter hoisting the movable machine room to a first transport position; and thereafter mounting the movable machine room to the first transport position in the hoistway vertically supported on stationary structures; and thereafter using the elevator car for transporting passengers and/or goods below the movable machine room while the machine room is mounted in said first transport position and the elevator car and the counterweight hang suspended from the machine room by the hoisting roping; and thereafter hoisting the movable machine room upwards to a second transport position; wherein the second transport position is higher than said first transport position; and thereafter mounting the movable machine room to the second transport position in the hoistway vertically supported on stationary structures; and thereafter using the elevator car for transporting passengers and/or goods below the movable machine room while the movable machine room is mounted in said second position.