A problem to be addressed by the present invention is to provide a carbon
fiber bundle capable of efficiently transiting the tensile strength of the
fiber to a carbon
fiber-reinforced
composite material formed using the carbon
fiber bundle, the carbon
fiber bundle including a
sizing agent added thereto, wherein the tensile strength of resin-impregnated strands (tensile strength A' of resin-impregnated strands) of the carbon
fiber bundle is 5.0 GPa or more and 6.0 GPa or less, as evaluated on the basis of JIS R7608 (2007) using Resin Formulation A below; wherein the tensile strength of resin-impregnated strands (tensile strength B' of resin-impregnated strands) of the carbon fiber bundle is 4.7 GPa or more and 5.5 GPa or less, as evaluated on the basis of JIS R7608 (2007) using Resin Formulation B below; wherein the ratio of the tensile strength B' of resin-impregnated strands to the tensile strength A' of resin-impregnated strands is 85% or more; and wherein the single-
fiber diameter of the carbon fiber bundle is 6.0 µm or more; Resin Formulation A: "CELLOXIDE (
registered trademark)" 2021P,
boron trifluoride monoethyl amine, and
acetone are used at a ratio of 100:3:4 (parts by
mass), and the curing conditions of a normal pressure, a temperature of 125°C, and a time of 30 minutes are used; and Resin Formulation B: "JER (
registered trademark)" 828, dicyandiamide, and 3-(3,4-dichlorophenyl)-1,1-
dimethylurea are used at a ratio of 100:6.3:2 (parts by
mass), and the curing conditions of a normal pressure, a temperature of 130°C, and a time of 90 minutes are used.