Abstract: A methyl methacrylate syrup is produced by the steps of (1) preparing a starting material comprising methyl methacrylate or a monomer mixture mainly comprising methyl methacrylate, and dividing the starting material into 20 to 70% by weight of an initial charge and 30 to 80% by weight of an after-charge; (2) heating the initial charge in a reactor; (3) adding a whole protion of a chain transfer agent at the time when the initial charge reaches a reaction temperature; (4) adding the after-charge over 0.1 to 10 hours together with a polymerization initiator having a half-life of 10 to 300 seconds at the reaction temperature; (5) continuing the heating after the addition of the after-charge and the polymerization initiator is complete; and (6) adding a hindered phenol polymerization inhibitor at the time the heating is finished. The methyl methacrylate syrup thus produced is excellent in storage stability.