This apparatus performs search for a bit plane where the first significant coefficient appears, as preprocessing of EBCOT coding processing of JPEG2000. This apparatus has a register for holding bit position data for each code block. In this apparatus, a code block of absolute value data of each inputted wavelet coefficient is identified and OR of the inputted absolute value data and the bit position data stored in the register is calculated. In this apparatus, the result of the calculation is stored again into the register as new bit position data. In this apparatus, the above-described OR calculation is performed to all the data in a wavelet transform area as a coding target, and the most significant bit plane of bit planes including a bit having a valid value is calculated for each block on the basis of the ultimately obtained bit position data.