The present invention improves the long-term storage stability of a polymerizable composition including an organoborane and a polymerizable monomer. A polymerizable composition includes (A) an organoborane, (B) an acidic group-free polymerizable monomer, and (C) a stabilizer for the organoborane (A), the composition being such that when the composition, after being allowed to stand at 45°C for 48 hours, is analyzed with an E-type viscometer at a temperature of 25°C and a rotational speed of 50 rpm, the ratio of the viscosity after the standing to the viscosity before the standing (viscosity after standing/viscosity before standing) is less than 100.
