A prepreg includes a resin composition or a semi-cured product of the resin composition, and a glass cloth, wherein the resin composition contains a modified polyphenylene ether compound terminally modified with a substituent having an unsaturated carbon-carbon double bond, and a crosslinkable curing agent having an unsaturated carbon-carbon double bond in a molecule, a content of the modified polyphenylene ether compound is 40 to 90 mass % with respect to a total mass of the modified polyphenylene ether compound and the crosslinkable curing agent, a cured product of the resin composition has a relative permittivity of 2.6 to 3.8, the glass cloth has a relative permittivity of 4.7 or less and a dielectric loss tangent of 0.0033 or less, and a cured product of the prepreg has a relative permittivity of 2.7 to 3.8 and a dielectric loss tangent of 0.002 or less.