Japanese wooden buildings are vulnerable to large earthquakes, and ensuring their seismic safety is a significant issue. However, many owners of wooden buildings hesitate to install seismic reinforcement because of the long construction period and high expense. There are many sliding doors in wooden buildings, which can be used for efficient seismic reinforcement. The objective of this study is to develop a seismic fitting for Japanese wooden buildings. Full-scale lateral loading tests were conducted for wooden frames that include a seismic fitting. The fittings can be constructed quickly and at a low cost. The parameters of the full-scale lateral loading tests were chosen in order to examine the effect of the fitting and the restriction condition surrounding a fitting on the seismic performance of a wooden frame. The relationships between the lateral load and deformation angle, the collapse mechanism, and the quantitative effect of seismic reinforcement for a wooden frame were clarified. From the results of the full-scale tests, it is found that the lift up of a seismic fitting should be restricted by a hanging wall for the seismic reinforcement of wooden frames.