2. The data compression method according to claim 1 , wherein the candidate acquiring unit further includes: taking the first candidate as the evaluation value; and comparing the stored value acquired from the recent match position list and the evaluation value with each address subsequent to the coding position being taken as an address and, when the acquired stored value is the value previous to the evaluation value, acquiring one or a plurality of subsequent candidates in order of increasing distance from the coding position, and in the match detecting unit, each of character strings starting at the first candidate and the subsequent candidates and the character string starting at the coding position are compared, and a character string having the longest match length is acquired and coded.
2. The data compression method according to claim 1 , wherein the candidate acquiring unit further includes: taking the first candidate as the evaluation value; and comparing the stored value acquired from the recent match position list and the evaluation value with each address subsequent to the coding position being taken as an address and, when the acquired stored value is the value previous to the evaluation value, acquiring one or a plurality of subsequent candidates in order of increasing distance from the coding position, and in the match detecting unit, each of character strings starting at the first candidate and the subsequent candidates and the character string starting at the coding position are compared, and a character string having the longest match length is acquired and coded. 3. The data compression method according to claim 2 , wherein in the candidate acquiring unit, when the subsequent candidate is acquired, a value of the acquired subsequent candidate is taken as an evaluation value for acquiring a next subsequent candidate.