An apparatus 10 for generating wartermark signals to be embedded as a digital watermark in real-time contents includes: input means 12 for inputting the real-time contents; an input buffer 14 for storing the real-time contents; generation means for generating wartermark signals corresponding to predicted intensities of the real-time contents from divided real-time contents; and an output buffer 18 for storing the generated wartermark signals to be outputted. The generation means is configured by including prediction means 16 for predicting intensities of the wartermark signals; control means 20 for controlling embedding by use of a message to be embedded as the digital watermark in the divided real-time contents; and means 22 for generating the wartermark signals to be outputted.