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Mental stress is closely connected with our physical and mental wellness. Therefore, stress measurement can contribute to assess our lifestyle and increase our quality of life. In this paper, we detect the secretory immunoglobulin A (sIgA), which is the candidate of salivary stress markers, with original electrochemical immunoassay: gold-linked electrochemical immunoassay (GLEIA). This biosensor is based on a sandwich-type immunosensor and adopts the electrochemical method to detect the reduction peak from Au nanoparticles linked to the secondary antibody. GLEIA is convenient and cost-effective that only requires a low sample volume (10 μL). In addition, the GLEIA show high sensitivity and selectivity. We obtained the linear response to relate the concentration of sIgA (10–300 ng/mL) in D-PBS buffer with the artificial saliva which includes salivary inorganic salt and typically glycoprotein (mucin). Furthermore, we obtained acceptable selectivity in the various solution with salivary proteins such as α-amylase, human serum albumin, immunoglobulin G (IgG), lysozyme, and mucin. In the future, we try to detect the sIgA in real saliva for on-site stress measurement using GLEIA and to integrate the various immunosensors for stress markers in saliva.