Provided is a sizing agent-coated carbon fiber bundle having excellent mechanical properties when used as a carbon fiber-reinforced composite material, a process for producing the same, a prepreg using the same, and a carbon fiber-reinforced composite material excellent in mechanical properties. A carbon fiber bundle coated with a sizing agent comprising a polyether type aliphatic epoxy compound and / or a polyol type aliphatic epoxy compound having two or more epoxy groups in the molecule or a water insoluble compound having a glass transition temperature of -100 DEG C to 50 DEG C, (Width / thickness) of the cross section of the bundle is not less than 10 but not more than 150, and when the carbon fiber bundle is divided into three parts in the width direction and in the mass direction along the fiber direction, the sizing to the mass of the carbon fiber bundle at the center and both ends Wherein the ratio of the amount of the sizing agent adhered at both ends / central portion calculated from the weight ratio of the sizing agent to the sizing agent is 1.05 or more and 1.5 or less.
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