A projection method, which is executed by a projection device, for projecting drawing data for a building onto a projection plane of the building under construction includes: measuring a distance from each of three or more points which are not aligned in a straight line and are on either of two non-parallel straight lines on the projection plane to the projection device using a distance meter included in the projection device; and projecting the drawing data onto a projection position on the projection plane which is determined based on the distance measured and the angle of the distance meter at the time at which the distance is measured.