This paper presents a method which detects events from floating car data (FCD). In traffic prediction, an event is one of unexpected factors which deteriorates the prediction performance. If occurrences of events are provided to prediction system beforehand, the prediction will be improved. Firstly, we confirmed contribution of event information to a traffic prediction accuracy. Then the paper will show that spatio-temporal pattern of zonal traffic attraction and generation is an intelligible trail of an event. Finally, the paper will propose an event detection and prediction method using PCA and HMM. The result shows feasibility of event prediction in high accuracy in certain condition.