An encoder encodes moving image data and generates encoded moving image data. A transmission buffer accumulates the encoded moving image data. A transmission/reception unit transmits the encoded moving image data to an image reception device via a wireless communication line. A failure detector predicts whether or not the failure of a real-time transmission of the encoded moving image data occurs, and detects the time until the failure occurs. When the failure is predicted to occur, an encoding controller controls the encoder to decrease, within the detected time, the target bit rate when the encoder encodes the moving image data.