To simply calculate a loaded weight by constituting a loaded weight- measuring instrument interposed between a load-carrying platform of a vehicle and a wheel, of a base body mounted to one of the platform and the wheel and a moving element graduated in a longitudinal direction which is set to the other of the base body and the wheel and is slidably fitted to the base body.

An upper end of a base body 18 is mounted at a bottom face of a load-carrying platform, and a lower end of a moving element 20 is kept in touch with a wheel 16. The load-carrying platform is lowered as a weight on the load-carrying platform increases, and therefore a fit distance of the base body 18 and moving element 20 is shortened. Since the lowered amount corresponds to the weight loaded on the platform, a scale 22 at the time is read and converted to a loaded weight. Suitable numeric values or numeric values converted to weights, etc., are preferably indicated on the scale 22. A weight loaded on the load-carrying platform of the vehicle can thus be measured readily and quickly in a simple constitution of the base body 18 and moving element 20. Overloading is prevented more effectively than when the loaded weight-measuring instrument is used at the loading time.