A format conversion method for converting a stream in a first format and including audio information, image information or management information into a stream in a second format, wherein the streams in the first and the second formats are respectively comprised of a plurality of unit data, and a first fixed byte length of data units of the first format is longer than a second fixed byte length of data units of the second format, the plurality of unit data in the first format is converted without having to be re-encoded into the plurality of unit data in the second format, and the stream in the first format has first reference value in the header of each of the plurality of unit data wherein, the first reference value is for setting or correcting a value of reference synchronizing information serving as a time reference to a value contemplated on an encoder, wherein the format conversion method includes: extracting a data length required in a first one of the plurality of unit data among the stream in the first format by comparing first reference values corresponding to a first one of the plurality of unit data and a next one of the plurality of unit data respectively, among the stream in the first format, the first one is a reference value of a pack used for storing the management information and the next one is a reference value of a pack used for storing the image information; appending unnecessary data to a first unit data including the management information in the second format to make the reference value of a second unit data in the second format correspond to the reference value of the pack used for storing the image information in the first format, wherein the unnecessary data is stuffed so that the data length of the first unit data including the management information in the second format and the calculated data length have a uniform length; and for a respective unit data of the first format used for storing image information or audio information: extracting a picture size of the payload portion of the respective unit data including the image information or the audio information; calculating a number of data dividable relative to a data size of the unit data of the second format; dividing data including the image information or the audio information in the respective unit data of the first format based on the number of data so as to allocate the divided data to units data of the second format. extracting a data length required in a first one of the plurality of unit data among the stream in the first format by comparing first reference values corresponding to a first one of the plurality of unit data and a next one of the plurality of unit data respectively, among the stream in the first format, the first one is a reference value of a pack used for storing the management information and the next one is a reference value of a pack used for storing the image information; appending unnecessary data to a first unit data including the management information in the second format to make the reference value of a second unit data in the second format correspond to the reference value of the pack used for storing the image information in the first format, wherein the unnecessary data is stuffed so that the data length of the first unit data including the management information in the second format and the calculated data length have a uniform length; and for a respective unit data of the first format used for storing image information or audio information: extracting a picture size of the payload portion of the respective unit data including the image information or the audio information; calculating a number of data dividable relative to a data size of the unit data of the second format; dividing data including the image information or the audio information in the respective unit data of the first format based on the number of data so as to allocate the divided data to units data of the second format. extracting a picture size of the payload portion of the respective unit data including the image information or the audio information; calculating a number of data dividable relative to a data size of the unit data of the second format; dividing data including the image information or the audio information in the respective unit data of the first format based on the number of data so as to allocate the divided data to units data of the second format.