To provide a bit conversion circuit, transfer unit, communication system, bit conversion method and program which implement a conversion table of bit conversion in a small gate scale.

According to 8b/10b encoder 11, for example, pattern classification of an encode table used in the case of 8b/10b conversion is performed in accordance with whether the number of '0' and '1' which the data after conversion has is the same, Then, when input data is a D code indicating data, the calculation is carried out by use of the number of input data being the same in the case where the number of '0' and '1' is the same, and otherwise, after conversion of one side polarity is performed according to the encode table, conversion of the other side polarity is performed by an inverter.