Provided are: a prepreg with low dielectric constant, low dielectric loss tangent, and improved adhesiveness to glass cloth; and a laminate for a circuit board. The prepreg is formed of the glass cloth serving as a base material and a semi-cured product of a thermosetting resin composition impregnated into the glass cloth, where the glass cloth comprises a treated surface treated by at least one type of silane coupling agent selected from methacryl-based silane coupling agents, acryl-based silane coupling agents, and isocyanate-based silane coupling agents, and the thermosetting resin composition contains polyphenyleneether having a terminal hydroxyl group modified with an ethylenically unsaturated compound in a main chain of the polyphenyleneether. The laminate for the circuit board is obtained by laminating the prepreg and a conductor layer.