Disclosed is a device and method for measuring the magnitude of a seepage force and its influence on effective stress of a formation. The measuring device includes a lower bearing platform having a pressure testing device fixed on an upper part thereof, and a water storage chamber mounted with a seepage water discharge pipe. A confining pressure loading chamber is mounted on the upper part of the lower bearing platform, and the lower bearing platform is used for placing a sample which has 11 measuring points distributed at equal intervals on an outer wall thereof. An upper and a lower permeable pressure-bearing steel sheet are placed on an upper and a lower end surface of the sample, respectively. The invention can improve the validity and accuracy of measurement and make the calculation result of the test more accurate.