One aspect of the present invention relates to a prepreg having a thermosetting resin composition or a semi-cured product of a thermosetting resin composition, and a fibrous base material, in which the thermosetting resin composition contains (A) a thermosetting resin containing a modified polyphenylene ether compound, (B) a first inorganic filler in which a molybdenum compound is present on at least a part of the surface, and (C) a second inorganic filler, a content of (B) the first inorganic filler is 0.1 parts by weight or more and 15 parts by weight or less, and a content of (C) the second inorganic filler is 200 parts by mass or less, with respect to 100 parts by weight of (A) the thermosetting resin, and the fibrous base material is a glass cloth containing quartz glass yarn.