A sample analyzer optically measures reaction of a sample mixed with reagent, and obtains optical information therefrom; generates a reaction curve representing change in the optical information over time; determines a first area prior to an evaluation target time (t0) and a second area after the evaluation target time (t0) wherein the first and second areas are formed between a baseline which is parallel to the time axis and a reaction curve from a first time (t1) prior to the optional evaluation target time (t0) to a second time (t2) after the evaluation target time, and determines the reaction end point based on the first and second areas; and obtains a characteristic of a sample based on the determined reaction end point, is disclosed. a sample analyzing method is also disclosed.