To improve the recovery efficiency of sludge from the filter of an electric discharge machine.

This filter is an internally and externally pressurizing type filter for an electric discharge machine, wherein the filter has a cylindrical shape as a whole and is for removing sludge in a working liquid for an electric discharge machine by passing the working liquid from the inner circumferential side to the outer circumferential side and from the outer circumferential side to the inner circumferential side. The filter is provided with an inner cylinder formed in the center part, filtration paper 11, 12 concentrically installed in the circumference of the inner cylinder, a pair of end plates 21, 31 installed in both ends in the axial direction of the filtration paper 11, 12, and a plurality of spacers interposed between the end plate 31 and an inner side end plate 25 for keeping a space to be a part of a circulation route for a working liquid. A reinforcing member is formed into a shape suiting with the filtration paper 12 in the radius direction and works as a guide at the time of discharging sludge.