To obtain a filter for a photographic developing machine which has high filtering accuracy although the filter shows small pressure loss and which can efficiently separate and filter a foreign matter in a treating tank by sintering a thermoplastic plastic material into a porous filter to have each specified porosity and pressure loss.

As for the thermoplastic plastic material to constitute the plastic filter for a photographic developing device, a ultrahigh mol.wt. polyethylene having an extremely small melt flow rate as ≤1.0, preferably ≤0.01 is used in a powder state having 50 to 700μm average particle size. The thermoplastic plastic material is sintered to obtain a film having 30 to 60vol% porosity filtering accuracty which collects foreign matters in ≥30μm size and ≤20mm Aq pressure loss under 1m3/m2.min flow amt. of dry air. It is preferable that the plastic filter has enough strength against compressive stress.