Building structure information is essential for achieving various indoor location-based services (ILBSs). Our approach integrates a large amount of pedestrian trajectories acquired by pedestrian dead reckoning (PDR) for generating a pedestrian network structure. To generate highly accurate pedestrian network structures, the accuracy of each trajectory must be improved. In this paper, we propose a method to improve the accuracy of indoor PDR trajectories by using many such trajectories. First, we select reliable trajectories based on the stability of the sensing data. Next by analyzing the trend of the step lengths, we correct the length of the trajectories. Finally, with same-route trajectories, we generate average trajectories for each route. We experimentally used HASC-IPSC and found that our proposed method improved the accuracy of the trajectories. The cumulative error rate of the original pedestrian trajectories was 0.1111m/s. After adapting our proposed method, the rate improved to 0.0622m/s.