To provide a liquid chromatograph preventing broadening of a detection peak of chromatogram and preventing deterioration of sensitivity, and to provide an analytical method using the same.

The liquid chromatograph includes: a moving phase liquid sending part that sends a moving phase; an injector for injecting a sample into the moving phase; a separation part for separating the sample; a reaction reagent liquid sending part for sending reaction reagent to the moving phase after passing through the separation part; a joint part for mixing the moving phase after passing through the separation part with the reaction reagent; a pipe where the moving phase and the reaction reagent after the mixing pass through; and a detector for detecting the sample reacted with the reaction reagent. The inside diameter of the pipe of the liquid chromatograph is 0.1 mm or less. An analytical method of the sample is a post-column method using the liquid chromatograph.