SUMMARYElectronic watermarking has drawn attention as a way to prevent or limit unauthorized copying of digital contents and has been studied and improved extensively. In this paper, as an improved version of the electronic watermarking method proposed by Cox, a method is proposed in which a pseudorandom number sequence is embedded as watermarking information into the wavelet coefficients of the image. In this method, two conventional schemes known as improvements of Cox's method are included. With regard to this electronic watermarking scheme, the detection accuracy of the watermarking information and the quality of the image with watermarking are analyzed. It is shown that the detection accuracy of the watermarking information is better than in the conventional scheme. This conclusion is verified by numerical experiments.