A manufacturing method of a filter is provided. The manufacturing method includes steps as follows. First, a substrate is provided and a black matrix is formed on the substrate. The black matrix has a number of openings arranged in array. Next, a filter material is individually formed in the openings by inkjet printing or other methods, and the filter material includes a solvent and a dye mixed with the solvent. Thereafter, a thermal treatment is performed and an evaporation rate of the solvent during the thermal treatment is reduced, so as to cure the filter material. As the evaporation rate of the solvent is relatively slow, the filter material is still flowable during the thermal treatment. Hence, the cured filter material has a flat surface. The filter fabricated by the above manufacturing method has an even hue and a well flattened surface.