Recently, the trend of miniaturization of electronic components is accelerated due to the spread of mobile devices. In particular, Multi-Layer Ceramic Capacitor (MLCC), made by stacking Ni paste layers and ceramic slurry layers alternately followed by a high-temperature sintering process, has a layer thickness of less than 1 μm. One of the biggest issue in MLCC is difference in sintering behavior between ceramic and metal layer and subsequent twisting or fracture due to that. In order to identify the origin of such problem and reduce it, a quantitative tool for analyzing the sintering behavior of the thin film form is required. However, at present, the analysis of sintering behavior of μm scale thin films is limited to indirect methods such as ex-situ microstructure change analysis. In this study, the sintering behaviors in thin film of Ni nanoparticle were successfully analyzed by measuring the stress variation of thin films using laser based optical analysis. First, a Ni paste of 80nm particles was applied evenly on a ceramic substrate by spin coating and it was heated up to 580°C in a chamber filled with N2 gas mixed with H2 gas for preventing oxidation. In this process, the stress curve versus temperature with 4 inflection points was obtained. Among them, the points related to the evaporation and decomposition of the solvents in the paste were excluded by comparison with the TGA data, and only one inflection point near 430°C remained. Then the microstructural analysis was carried out for the samples quenched at the temperatures below and above the point. Finally, it was found that the inflection point has a significant relation with the neck formation in the sintering process. The same results were obtained for Ni-alloy materials. This study suggests a method of in-situ analysis of the sintering behavior of metal nanoparticles through stress analysis, and it is expected to act as useful guide line for the study of materials requiring high-temperature sintering process.