Method for manufacturing expandable microspheres, and expandable microspheres

To provide: a method for manufacturing expandable microspheres with which the start of a polymerization reaction in an oil phase at an unintended time such as while a dispersion is being prepared or prior to the start of polymerization is suppressed, the intended polymerization reaction in an oil phase is not hindered, and properties such as expansion ratio are exceptional; and expandable microspheres having excellent properties. A method for manufacturing expandable microspheres in which a foaming agent is sealed in the outer shell of a produced polymer and in which the maximum expansion ratio is 5 or higher, the method being characterized in that at least the foaming agent, a polymerizable monomer, a polymerization initiator, and a water-soluble polymerization inhibitor or a non-water-soluble polymerization inhibitor are suspended in an aqueous dispersion medium whereupon suspension polymerization is performed in the presence of the water-soluble polymerization inhibitor or the non-water-soluble polymerization inhibitor.