Vinyl polymer powder, thermoplastic resin composition, and molded body thereof

This vinyl polymer powder, which contains a vinyl polymer, has a glass transition temperature of at least 0 DEG C (where if there are a plurality of glass transition points, all of the glass transition temperatures are at least 0 DEG C), has no greater than 350 ppm of the total content of magnesium ions, calcium ions, aluminum ions, barium ions, and zinc ions, has no greater than 100 ppm of the content of ammonium ions, has an acid number of no greater than 2.5 mgKOH/g, and has a bulk density of 0.10-0.60 g/cm3.