PREPREG

The present invention addresses the problem of providing a prepreg that yields a carbon fiber composite material that has exceptional tensile strength, heat resistance, and impact resistance and is suitable as a structural material of an aircraft body, wherein the resin composition used in the prepreg furthermore has exceptional viscosity stability. A prepreg containing a resin composition that contains carbon fibers and at least the constituent elements [A]-[D] indicated below, wherein: the epoxy resin of constituent element [A] contains [A1] and [A2]; [A1] has an epoxy equivalent of 200-265 g/eq (inclusive), the [A1] content of constituent element [A] being 5-45 parts by mass (inclusive); the [A2] content is 55-95 parts by mass (inclusive); [A2] includes at least [A2-1] and [A2-2]; the ratio [A2-1]/[A2-2] is 0.7-4.0 (inclusive) by mass; and the viscosity increase rate when the resin composition is held for two hours at 80°C is 20% or less. Constituent element [A] is an epoxy resin including [A1] and [A2], constituent element [A1] is a dicyclopentadiene epoxy resin, constituent element [A2] is an epoxy resin containing [A2-1] and [A2-2], constituent element [A2-1] is a tetrafunctional liquid epoxy resin, constituent element [A2-2] is a bifunctional liquid epoxy resin, constituent element [B] is a diaminodiphenyl sulfone, constituent element [C] is a polyether sulfone, and constituent element [D] is aspherical polymer particles.