Abstract: The device for simultaneous weighing and agitation comprises a tray (14) for receiving an object (15) to be weighed, which object is a receptacle (15) for progressively receiving a substance (18), and the tray (14) is associated both with means (16) enabling the weight of said object to be measured, and with means (1) enabling agitation motion to be imparted thereto. The tray (14) and the agitation means (1) are mounted on a common support (17) on which exact measurement is then performed with an error of not more than 5% of the weight of the combined device and object (15) to be weighed during agitation.