Formaldehyde has a general toxic action on the living organisms and is one of the priority pollutants of the atmospheric air of the urban area of the Russian Federation. In this regard, monitoring the content of formaldehyde in atmospheric precipitation is of interest both for studying the level of ambient air pollution and assessing the impact on natural surface waters. The purpose of this work is to study the seasonal and annual concentration of formaldehyde in the atmospheric precipitation and atmospheric deposition on the underlying surface of South-Western Siberia (on the example of Barnaul). The paper presents the results of the fluorimetric analysis of the formaldehyde in the wet atmospheric precipitation (rain, snow) of Barnaul, collected from May 2014 to December 2021. Formaldehyde concentration varies widely and is subject to seasonal change. The weighted average concentration of formaldehyde during the study period was 0.1 mg/L. There is a gradual decrease in the formaldehyde concentration in the atmosphere air of Barnaul, which still remains at a fairly high level. Based on the data obtained, the atmospheric deposition of formaldehyde was calculated onto underlying surface, which amounted to 0.04 g/m2.