The present invention provides a stabilized (meth)acryloyloxyalkyl isocyanate, a process for stabilization thereof and a process for preparation of the same. More particularly, it provides a (meth)acryloyloxyalkyl isocyanate having a small hydrolyzable chlorine content and good storage stability, a process for stabilizing a (meth)acryloyloxyalkyl isocyanate prepared using phosgene which process comprises decreasing the amount of a hydrolyzable chlorine with purification and a process for preparation of a stabilized (meth)acryloyloxyalkyl isocyanate. An acidic gas such as carbon dioxide or the like was forcedly dissolved in (meth)acryloyloxyalkyl isocyanate, particularly (meth)acryloyloxyalkyl isocyanate which content of hydrolyzable chlorine is decreased with purification and thereby the storage stability of the (meth)acryloyloxyalkyl isocyanate is improved.