Abstract: The present invention relates to a amyotrophic lateral sclerosis (ALS) diagnostic composition using acid sphingomyelinase (ASM), and a method for detecting diagnostic markers and, more specifically, to a method and a composition for detecting markers for ALS, the method comprising the steps of: (a) providing a sample of a subject; (b) measuring the ASM expression level or the enzyme activation level in the sample; (c) determining that a subject, of which the ASM expression level or the enzyme activation level is increased compared to that of a normal person, has ALS. According to the investigation of the present inventors, the activity of ASM, among lipids and enzymes related to the sphingolipid metabolism, is specifically increased in a sample of an ALS patient compared to that of a normal person. ASM can be used as a marker for diagnosing ALS, thereby enabling the development of a novel and effective diagnostic reagent.