Breast cancer, despite its high incidence, exhibits significantly improved survival rates when diagnosed at an early stage. Consequently, rapid and accurate diagnosis is crucial for managing breast cancer. In this paper, we present the development of a lateral flow immunoassay device for the swift diagnosis of breast cancer by detecting thioredoxin 1, a novel biomarker for early breast cancer detection. To improve the sensitivity of the device, we utilized the enzyme mimetic nanoparticle, H-Pt-Nanozyme, as a detection label, potentially allowing signal amplification through enzyme reactions. Adjusting the detection range for breast cancer qualitative diagnosis based on the previously proposed cut -off value of 11.4 ng/mL, the optimized device demonstrated similar sensitivity and superior reproducibility compared to device using gold nanoparticles, a commonly used detection label, under the same conditions. The developed device successfully differentiated between 10 breast cancer patients and 10 healthy individuals by naked-eye detection. Finally, to prevent false -negative diagnosis, we confirmed the feasibility for signal amplification through the utilization of enzyme reactions. The device developed in this study allows for the effective discrimination of early-stage breast cancer patients, reducing false -negative rates associated with mammography and ultrasonography, the current gold -standard diagnostic methods according to breast cancer diagnosis and screening guidelines. Additionally, its potential to assist in clinical suspicion in clinical settings raises expectations for preventing unnecessary surgeries in false -positive cases.