A prepreg, comprising: a reinforcing fiber; and an epoxy resin composition, wherein the G'Tg of the cured material of the prepreg is 150°C or higher when the prepreg is cured by being pressed and kept for 5 minutes in a die preheated at 140°C under a pressure of 1 MPa, and wherein the epoxy resin composition comprises component and Component, and at least either component or component: Component: an epoxy resin that does not include a sulfur atom in the molecule; Component: an imidazole compound represented by formula below; Component: an imidazole compound represented by formula below; Component: an epoxy resin that includes at least one sulfur atom in the molecule; wherein R 1 indicates a straight-chain or branched-chain alkyl group or hydroxymethyl group having 1∼5 carbon atoms, and R 2 indicates a hydrogen atom or a straight-chain or branched-chain alkyl group having 1∼5 carbon atoms; wherein R 3 indicates an organic group containing at least one carbon atom, and R 4 ∼R 6 indicate a hydrogen atom, a methyl group or an ethyl group; wherein the G'Tg of the cured material of the prepreg is determined as follows: a resin sheet is cut into test pieces (55 mm long x 12.5 mm wide), and the values of log G' are plotted in relation to temperature using a Rheometer ARES-RDA, made by TA Instruments, under conditions of a frequency of 1 HZ and a programmed rate of temperature rise of 5°C/min. The temperature at a point where the approximate straight line in a flat region of log G' crosses the approximate straight line in a region where log G' declines drastically is determined as the glass transition temperature (G'Tg). a reinforcing fiber; and an epoxy resin composition, wherein the G'Tg of the cured material of the prepreg is 150°C or higher when the prepreg is cured by being pressed and kept for 5 minutes in a die preheated at 140°C under a pressure of 1 MPa, and wherein the epoxy resin composition comprises component and Component, and at least either component or component: Component: an epoxy resin that does not include a sulfur atom in the molecule; Component: an imidazole compound represented by formula below; Component: an imidazole compound represented by formula below; Component: an epoxy resin that includes at least one sulfur atom in the molecule; Component: an epoxy resin that does not include a sulfur atom in the molecule; Component: an imidazole compound represented by formula below; Component: an imidazole compound represented by formula below; Component: an epoxy resin that includes at least one sulfur atom in the molecule; wherein R 1 indicates a straight-chain or branched-chain alkyl group or hydroxymethyl group having 1∼5 carbon atoms, and R 2 indicates a hydrogen atom or a straight-chain or branched-chain alkyl group having 1∼5 carbon atoms; wherein R 3 indicates an organic group containing at least one carbon atom, and R 4 ∼R 6 indicate a hydrogen atom, a methyl group or an ethyl group; wherein the G'Tg of the cured material of the prepreg is determined as follows: a resin sheet is cut into test pieces (55 mm long x 12.5 mm wide), and the values of log G' are plotted in relation to temperature using a Rheometer ARES-RDA, made by TA Instruments, under conditions of a frequency of 1 HZ and a programmed rate of temperature rise of 5°C/min. The temperature at a point where the approximate straight line in a flat region of log G' crosses the approximate straight line in a region where log G' declines drastically is determined as the glass transition temperature (G'Tg). a resin sheet is cut into test pieces (55 mm long x 12.5 mm wide), and the values of log G' are plotted in relation to temperature using a Rheometer ARES-RDA, made by TA Instruments, under conditions of a frequency of 1 HZ and a programmed rate of temperature rise of 5°C/min. The temperature at a point where the approximate straight line in a flat region of log G' crosses the approximate straight line in a region where log G' declines drastically is determined as the glass transition temperature (G'Tg).