A process for producing acrylic acid of the present invention comprises the step of conducting gas-phase oxidative dehydrogenation of a composition containing propionaldehyde using a solid catalyst containing molybdenum and vanadium as essential components, thereby obtaining acrylic acid. The obtained acrylic acid is preferably purified by crystallization, and a monomeric component containing the purified acrylic acid is polymerized to thereby give a hydrophilic resin such as an absorbent resin and a water-soluble resin.