A work area setting and managing system which enables a operator to plan and manage work in a work area and set and store the work area at just the mobile work machine side at the work site is provided. The system is applied to a mobile work machine 11 performing land mine disposal work in the work area and provided with a GPS 3D position finding system and a tablet computer 62 having a display unit 63, input unit 64, and memory 65. This system is provided with a first means for displaying a work monitor screen 90 on a screen of the display unit, a second means for displaying a symbol of the mobile work machine on the work monitor screen based on positional coordinates of an attachment of the mobile work machine obtained by the GPS 3D position finding system, and a third means for preparing a work area based on an input operation of a operator using as the origin the symbol displayed on the work monitor screen and displaying a work area block model showing the work area.