A working machine (1, 1A) comprising: a traveling body that travels; a swing body mounted to the traveling body to be swingable; a working front mounted to the swing body to be rotatable; a design data obtainment unit configured to obtain design data that has topographical data after completion of construction in the form of three-dimensional data; a topography measuring device configured to measure surrounding topographical data in the form of three-dimensional data; and a controller having a design data processor configured to process the topographical data obtained by the design data obtainment unit as a predetermined first coordinate system design data, a current topography data generator configured to generate current topography data of the second coordinate system from the topography data measured by the topography measuring device, the second coordinate system being defined based on the installation position of the topography measuring device, and a position/posture estimation unit configured to estimate a self-position and posture in the second coordinate system based on the current topography data generated by the current topography data generator, the controller being configured to extract peripheral area shape data from the first coordinate system design data, map similar shape portions between the extracted peripheral area shape data and the current topography data, calculate a coordinate transformation matrix to transform from the second coordinate system to the first coordinate system so that the difference in coordinate values of the mapped shape portions is minimized, and transform the self-position and posture of the working machine (1, 1A) and the current topography data from coordinates in the second coordinate system to coordinates in the first coordinate system using the calculated coordinate transformation matrix. a traveling body that travels; a swing body mounted to the traveling body to be swingable; a working front mounted to the swing body to be rotatable; a design data obtainment unit configured to obtain design data that has topographical data after completion of construction in the form of three-dimensional data; a topography measuring device configured to measure surrounding topographical data in the form of three-dimensional data; and a controller having a design data processor configured to process the topographical data obtained by the design data obtainment unit as a predetermined first coordinate system design data, a current topography data generator configured to generate current topography data of the second coordinate system from the topography data measured by the topography measuring device, the second coordinate system being defined based on the installation position of the topography measuring device, and a position/posture estimation unit configured to estimate a self-position and posture in the second coordinate system based on the current topography data generated by the current topography data generator, the controller being configured to extract peripheral area shape data from the first coordinate system design data, map similar shape portions between the extracted peripheral area shape data and the current topography data, calculate a coordinate transformation matrix to transform from the second coordinate system to the first coordinate system so that the difference in coordinate values of the mapped shape portions is minimized, and transform the self-position and posture of the working machine (1, 1A) and the current topography data from coordinates in the second coordinate system to coordinates in the first coordinate system using the calculated coordinate transformation matrix.