A filter apparatus includes a filter housing having a filter head (3) and a filter bowl (7). The housing accommodates a filter element that separates a non-filtrate side (15) from a filtrate side (17). A differential pressure measurement device (59) indicates at least a blockage of the filter element during filtration operation and has a measurement piston (91) that is guided in a measurement housing (88) in a longitudinally displaceable manner. An end face (90) of that piston is subjected to the instantaneous pressure of the non-filtrate side (15). The opposite end face of the piston is subjected to the instantaneous pressure of the filtrate side (17). Each instantaneous pressure passes into the measurement housing (88) via at least one conduit (57, 61, 65, 89). At least a section (57, 61) of the conduit is arranged in an element cap (43) of the filter element.