A program execution device comprising: program code storage means arranged to receive and store data that has been obtained by compressing a program code constituted by an execution code that is composed of process data used for an execution process and a command representing the execution process, wherein the compression of the program code has caused the data stored in the program code storage means to be structured so that it comprises a plurality of consecutive predetermined data amounts of process data followed by the command that represents the execution process that said plurality of consecutive predetermined data amounts of process data are used for, wherein each predetermined amount of process data has the same fixed amount of data; buffer storage means arranged to temporarily only store the process data related to the same command; code type determination means arranged to read the data, that has been obtained by compressing the program code, from the program code storage means by the predetermined data amounts, wherein each read of the data is a read of the same fixed amount of data, to determine whether or not the data contains the command, and to store the process data in the read data in the buffer storage means when it is determined as the data which does not contain the command; code extension means arranged to generate an execution code on the basis of the process data stored in the buffer storage means and the command when the code type determination means has determined that the data contains the command; and execution means arranged to sequentially perform the execution process of the program code by an interpreter on the basis of the execution code generated by the code extension means, wherein the same command is consecutively and independently executed, by the execution means, with each of the fixed amounts of process data that are stored in the buffer storage means. program code storage means arranged to receive and store data that has been obtained by compressing a program code constituted by an execution code that is composed of process data used for an execution process and a command representing the execution process, wherein the compression of the program code has caused the data stored in the program code storage means to be structured so that it comprises a plurality of consecutive predetermined data amounts of process data followed by the command that represents the execution process that said plurality of consecutive predetermined data amounts of process data are used for, wherein each predetermined amount of process data has the same fixed amount of data; buffer storage means arranged to temporarily only store the process data related to the same command; code type determination means arranged to read the data, that has been obtained by compressing the program code, from the program code storage means by the predetermined data amounts, wherein each read of the data is a read of the same fixed amount of data, to determine whether or not the data contains the command, and to store the process data in the read data in the buffer storage means when it is determined as the data which does not contain the command; code extension means arranged to generate an execution code on the basis of the process data stored in the buffer storage means and the command when the code type determination means has determined that the data contains the command; and execution means arranged to sequentially perform the execution process of the program code by an interpreter on the basis of the execution code generated by the code extension means, wherein the same command is consecutively and independently executed, by the execution means, with each of the fixed amounts of process data that are stored in the buffer storage means.