A working machine 1 includes a design data obtainment unit 29, a topography measuring device 30, and a controller 21. The controller 21 extracts peripheral area shape data from the design data in the construction-site coordinate system, maps similar shape portions between the extracted peripheral area shape data and the current topography data in the current topography coordinate system, calculates a coordinate transformation matrix to transform from the current topography coordinate system to the construction-site coordinate system so that a difference in coordinate values of the mapped shape portions is minimized, and transforms the self-position and posture of the working machine 1 and the current topography data from coordinates in the current topography coordinate system to coordinates in the construction-site coordinate system using the calculated coordinate transformation matrix.