In this paper, we present a Spatiotemporal Generative Adversarial Network (STGAN)-based model that accurately detects traffic anomalies using data from 42 traffic cameras in Gothenburg, Sweden, in 2020. STGAN captures the complex spatial and temporal dependencies of traffic data by combining Graph Neural Networks and Long Short-Term Memory networks. Real-time traffic volume data in units of minutes are converted into flow indicators representing vehicle density, which are used as inputs to the model. The model is trained with data from April to November 2020 and validated with data from November 14 to 23. As a result, we demonstrate that the model effectively detects traffic anomalies (such as camera signal outages, visual artifacts, and extreme weather conditions) with high accuracy and low false positive rate.