This paper proposes a method of estimating a target-object shape, the location of which is unknown, through the use of location-unknown mobile distance sensors. The direction of the sensor is fixed from the moving direction. Typically, mobile sensors are mounted on vehicles. Each sensor continuously measures the distance from it to the target object. The estimation method does not require any positioning function, anchor-location information, or additional mechanisms to obtain side information such as angle of arrival of signal. Under the assumption of a polygon target object, each edge length and vertex angle and their combinations are estimated to completely estimate the shape of the target object.