A prepreg comprising: carbon fibers coated with a sizing agent; and a thermosetting resin composition impregnated into the sizing agent-coated carbon fibers, wherein the sizing agent includes an aliphatic epoxy compound and an aromatic compound at least containing an aromatic epoxy compound, wherein a mass ratio / of the aliphatic epoxy compound and the aromatic epoxy compound is 52/48 to 80/20, and preferably the sizing agent is a mixture of a water emulsion liquid containing at least the aromatic epoxy compound and a composition containing at least the aliphatic epoxy compound, and the sizing agent contains an ester compound having no epoxy group in a molecule in an amount of 2 to 35% by mass relative to the total amount of the sizing agent except the solvent; the sizing agent-coated carbon fibers have an (a)/(b) ratio of 0.50 to 0.90 where (a) is a height (cps) of a component at a binding energy (284.6 eV) assigned to CHx, C-C, and C=C and (b) is a height (cps) of a component at a binding energy (286.1 eV) assigned to C-O in a C 1s core spectrum of a surface of the sizing agent applied onto the carbon fibers analyzed by X-ray photoelectron spectroscopy using AlKα 1,2 as an X-ray source at a photoelectron takeoff angle of 15°, the sizing agent-coated carbon fibers are in a shape of woven fabric or braid, the thermosetting resin composition at least includes the following components:: a thermosetting resin;: a thermoplastic resin soluble to the thermosetting resin, the thermoplastic resin is preferably polyethersulfone and more preferably polyethersulfone having an average molecular weight of 15,000 to 30,000 g/mol; and: a latent hardener;: core-shell rubber particles that include particulate core parts and in which at least part of a surface of each of the core parts is covered with a shell, such shells of the core-shell rubber particles are preferably formed of a resin having a functional group that is capable of reacting with the latent hardener or a functional group that is capable of reacting with the thermosetting resin, a resin contained in the shells of the core-shell rubber particles preferably has an epoxy group, and a volume average particle diameter of the core-shell rubber particles is preferably 50 to 150 nm; wherein the stress intensity factor K1c of a thermosetting resin cured product obtained by curing the thermosetting resin composition is 0.65 to 1.5 MPa·m 1/2. carbon fibers coated with a sizing agent; and a thermosetting resin composition impregnated into the sizing agent-coated carbon fibers, wherein the sizing agent includes an aliphatic epoxy compound and an aromatic compound at least containing an aromatic epoxy compound, wherein a mass ratio / of the aliphatic epoxy compound and the aromatic epoxy compound is 52/48 to 80/20, and preferably the sizing agent is a mixture of a water emulsion liquid containing at least the aromatic epoxy compound and a composition containing at least the aliphatic epoxy compound, and the sizing agent contains an ester compound having no epoxy group in a molecule in an amount of 2 to 35% by mass relative to the total amount of the sizing agent except the solvent; the sizing agent-coated carbon fibers have an (a)/(b) ratio of 0.50 to 0.90 where (a) is a height (cps) of a component at a binding energy (284.6 eV) assigned to CHx, C-C, and C=C and (b) is a height (cps) of a component at a binding energy (286.1 eV) assigned to C-O in a C 1s core spectrum of a surface of the sizing agent applied onto the carbon fibers analyzed by X-ray photoelectron spectroscopy using AlKα 1,2 as an X-ray source at a photoelectron takeoff angle of 15°, the sizing agent-coated carbon fibers are in a shape of woven fabric or braid, the thermosetting resin composition at least includes the following components:: a thermosetting resin;: a thermoplastic resin soluble to the thermosetting resin, the thermoplastic resin is preferably polyethersulfone and more preferably polyethersulfone having an average molecular weight of 15,000 to 30,000 g/mol; and: a latent hardener;: core-shell rubber particles that include particulate core parts and in which at least part of a surface of each of the core parts is covered with a shell, such shells of the core-shell rubber particles are preferably formed of a resin having a functional group that is capable of reacting with the latent hardener or a functional group that is capable of reacting with the thermosetting resin,: a thermosetting resin;: a thermoplastic resin soluble to the thermosetting resin, the thermoplastic resin is preferably polyethersulfone and more preferably polyethersulfone having an average molecular weight of 15,000 to 30,000 g/mol; and: a latent hardener;: core-shell rubber particles that include particulate core parts and in which at least part of a surface of each of the core parts is covered with a shell, such shells of the core-shell rubber particles are preferably formed of a resin having a functional group that is capable of reacting with the latent hardener or a functional group that is capable of reacting with the thermosetting resin, a resin contained in the shells of the core-shell rubber particles preferably has an epoxy group, and a volume average particle diameter of the core-shell rubber particles is preferably 50 to 150 nm;