A material position information measuring section measures a position of a material lifted up by a tower crane. A structure information measuring section measures position information about surrounding structures. A route searching section searches for a route of movement of the material from a start point to a destination. The route of movement determined by the route searching section is stored in a route storage. A data processor receives data of the material position information measuring section and the structure information measuring section, and calculates 2D or 3D image data about relative positions of the tower crane, the material lifted up by the tower crane and the surrounding structures. A display unit displays information about at least one of the tower crane, the material and the surrounding structures using the image data calculated by the data processor, and displays the route of movement determined by the route searching section.