Display omitted •The change of CA over time on laser micro-structured surfaces is investigated.•The relationship between CA and chemistry was discussed by model description.•The coefficients in the model were obtained by multiple regression analysis.•The reason for CA becoming high is related to the carbon and oxygen-(metal oxide).•The reason for CA keeping low is related to the effect of oxygen-(layer). In recent years, control of the wettability of metal surfaces by laser micro-structuring has attracted much attention. In particular, for applying to industrial applications, long-term stability of wettability is required for metal surfaces by laser micro-structuring, since the wettability of the surface changes over time. In this study, the influences of various chemical components on contact angle (CA) changes over time were quantitatively investigated using a model based on multiple regression analysis. For this purpose, this study investigated the CA and chemical components of laser micro-structured stainless steel 304 surfaces 40 and 80 days after laser micro-structuring. In the end, the reason for the CA becoming high was related to the carbon-C–C(C–H), carbon-(polar), and oxygen-(metal oxide). Moreover, the reason for the CA keeping low for a long time was related to the effect of oxygen-(layer).