A reversible data hiding scheme based on integer-to-integer wavelet transform is proposed in this paper. The scheme uses a Sudoku-based method to embed data by modifying the wavelet coefficients. First, the algorithm performs the one-level integer wavelet transform of the host image and obtains four sub-bands, i.e., LL1, HL1, LH1, and HH1. Then, the HL1 sub-band is used as the base matrix, and the LH1 sub-band is used as the variable matrix to embed the secret digits according to a Sudoku table. A location map is created to record the embeddable coefficients, and the map is embedded into the sub-band of HH1. The experimental results showed that our proposed scheme produced a higher-quality stego image than those existing hiding schemes.