The present invention provides a method of producing a suspension containing a nano-cocrystal having an average particle size of not more than 300 nm, a polymer having a number average molecular weight of not less than 3,000, a surfactant having a number average molecular weight of less than 3,000 and water, which method including wet grinding a cocrystal, which is constituted of an organic compound and a cocrystal former and is not dissociated by wet grinding, in water containing the polymer and the surfactant.