Influences of casting solvent on the microphase-separated structures of poly(2-vinylpyridine)-block-polyisoprene films were studied by transmission electron microscopy and small-angle X-ray scattering. The variations of the structures obtained were consequences of vitrification of microdomain structures developed during the solvent casting processes. The various microphase-separated structures were properly understood by considering the Hansen's solubility parameters of the solvent and the copolymer, which quantify the polymer-solvent interactions in the system.