The invention discloses a computer fan blade flatness detection device and a flatness detection method thereof. The computer fan blade flatness detection device includes: fan clamping and driving mechanisms each of which includes a fan support assembly used for supporting a fan and a blade rotating assembly used for rotating a fan blade; a one-dimensional code recognition device used for collecting one-dimensional code information of the fan supported on the fan support assembly; a distance measuring device used for collecting at least two sets of height distance information of a fixed point of a fan shell supported on the fan support assembly and height distance information of a measuring fixed point on the fan blade in a rotation process; and an upper computer which is in communication connection with the one-dimensional code recognition device and the distance measuring device. The computer fan blade flatness detection device provided by the invention can perform one-dimensional code scanning and measurement of the flatness of the computer fan blade at the same time, thereby improving detection efficiency.