Provided are a method of producing a photoresist comprising a process of filtrating a raw resist solution containing resist constituent components and a resist solvent dissolving them, using a filter made of at least one resin selected from fluorine-based resins and polyolefins, wherein this filter has been used for filtration of the same or different kind of other raw resist solution and has been washed with a solvent containing the resist solvent toward the reverse direction to the filtration direction, and a method of sequentially producing two or more photoresists using the same production apparatus, wherein this production apparatus is washed with the resist solvent, a solvent other than this resist solvent capable of dissolving or decomposing the resist constituent components, and the resist solvent, in this order, after production of the photoresist and before production of the subsequent photoresist.