A method for crystallization of acrylic acid, wherein the method is carried out using a crystallization unit to separate an acrylic acid-containing solution into a mother liquid and a purified acrylic acid, wherein said crystallization unit comprises: crystallizer having an exit to take out the mother liquid and the purified acrylic acid alternately; supply line to supply the acrylic acid-containing solution to said crystallizer; and recovery line which is connected to said exit and recovers the mother liquid and the purified acrylic acid alternately from the crystallizer; wherein said recovery line is equipped with an opening and closing unit; said method including the following steps (A) to (D): (A) crystallization step in which acrylic acid is crystallized by cooling the acrylic acid-containing solution supplied through said supply line in said crystallizer; (B) mother liquid recovery step in which the mother liquid obtained at said crystallization step is recovered from said recovery line by opening the opening and closing unit in said recovery line; (C) melting step in which after closing said opening and closing unit in said recovery line, acrylic acid is melted by heating up the crystal of acrylic acid obtained at said crystallization step; and (D) purified acrylic acid recovery step in which the purified acrylic acid obtained at said melting step is recovered from said recovery line by opening the opening and closing unit in said recovery line; characterized in that the opening and closing unit consists of a ball valve. crystallizer having an exit to take out the mother liquid and the purified acrylic acid alternately; supply line to supply the acrylic acid-containing solution to said crystallizer; and recovery line which is connected to said exit and recovers the mother liquid and the purified acrylic acid alternately from the crystallizer; wherein said recovery line is equipped with an opening and closing unit; said method including the following steps (A) to (D): (A) crystallization step in which acrylic acid is crystallized by cooling the acrylic acid-containing solution supplied through said supply line in said crystallizer; (B) mother liquid recovery step in which the mother liquid obtained at said crystallization step is recovered from said recovery line by opening the opening and closing unit in said recovery line; (C) melting step in which after closing said opening and closing unit in said recovery line, acrylic acid is melted by heating up the crystal of acrylic acid obtained at said crystallization step; and (D) purified acrylic acid recovery step in which the purified acrylic acid obtained at said melting step is recovered from said recovery line by opening the opening and closing unit in said recovery line; (A) crystallization step in which acrylic acid is crystallized by cooling the acrylic acid-containing solution supplied through said supply line in said crystallizer; (B) mother liquid recovery step in which the mother liquid obtained at said crystallization step is recovered from said recovery line by opening the opening and closing unit in said recovery line; (C) melting step in which after closing said opening and closing unit in said recovery line, acrylic acid is melted by heating up the crystal of acrylic acid obtained at said crystallization step; and (D) purified acrylic acid recovery step in which the purified acrylic acid obtained at said melting step is recovered from said recovery line by opening the opening and closing unit in said recovery line; characterized in that the opening and closing unit consists of a ball valve. <EOS>