The present invention relates to a plating layer test of a tin plate, specifically to an automatic sample treatment test apparatus for determining lead in a tin plate plating layer. The apparatus comprises: an electrolysis tank, wherein the electrolysis tank is filled with a stripping solution and is provided with a tin plate requiring determination; a sealing ring inserted and sleeved inside the electrolysis tank; a pneumatic sealing mechanism, wherein the pneumatic sealing mechanism comprises a pneumatic valve and a sealing execution rod; electrodes, wherein platinum wire is wound inside the electrolysis tank to be adopted as a work electrode, a silver electrode or a calomel electrode inserted into the electrolysis tank is adopted as a reference electrode, and a titanium alloy pin connected with the tin plate requiring determination is adopted as a sample electrode; a sample collection device communicated with the electrolysis tank; a set of liquid adding system, wherein the system comprises a chemical tank and a peristaltic pump; a set of flushing system, wherein the system comprises a distilled water tank, a pipeline connected with the electrolysis tank, and sprinklers; and a PLC control system for controlling switches for connecting the peristaltic pump, the pneumatic valve and a sample collector and a flushing switch. With the present invention, lead determination automation in the tin plate plating layer can be achieved, and determination precision and work efficiency can be improved.