The invention relates to an instrument for measuring the lower chest circumference comfortableness of a bra, which comprises a stand body with a storage battery, a transmission device, a measuring device, a data input and equipment control device and a data output device, wherein the transmission device, the measuring device, the data input and equipment control device and the data output device are respectively arranged on the back of the stand body with a storage battery; the transmission device, the measuring device and the data input and the equipment control device are electrically connected one another respectively through leads; the data output device is electrically connected with the data input and equipment control device through leads; and the storage battery of the stand body is electrically connected with the transmission device, the measuring device, the data input and equipment control device and the data output device respectively through leads. By the instrument, the invention, the effect of a human body wearing a bra product for a long time can be stimulated and the obtained test data is compared with the known wearing comfortableness data of a corresponding model of bra, and thus, whether the tested bra product reaches the specified lower chest circumference comfortableness indexes can be scientifically and accurately known.