Heat-expanding microspheres having adhesive properties, and method for producing same

Provided are heat-expanding microspheres characterized in that the expanded beads formed have excellent adhesion between one another and with other materials, there is minimal dislodgement of expanded beads, and the molding thus obtain has excellent mechanical properties. These heat-expanding microspheres having an expanding agent sealed inside the outer shell of a polymer are characterized by a retention rate of at least 3 mass % blower testing is performed, on a glass substrate, on expanded beads obtained by expanding said microspheres.