A method for transcoding a first data sequence generated by a first moving picture coding system to a second data sequence generated by a second moving picture coding system. The method comprises recording a code amount of a coding-unit in reading data of the coding-unit from said first data sequence; determining a target value of said generated code amount of said second data sequence on a coding-unit basis, said target value being obtained by multiplying a recorded code amount by a factor; and performing a rate control so that said generated code amount of said second data sequence comes close to said target value in generating said second data sequence from said data of the coding-unit with said second moving picture coding system, wherein a ratio of code amounts, on the coding-unit basis, of data composing said first data sequence is made close to a ratio of code amounts, on the coding-unit basis, of data composing said second data sequence corresponding to said first data sequence.