A program converter (1) converts a program (P) which performs arithmetic addition processing to execute encryption, into a converted program (tP) which performs processing equivalent to the processing of the program (P). The program converter (1) includes: a key data extraction unit (10) which extracts key data from the program (P); an addition table generation unit (11) which generates an addition table from the extracted key data; a conversion table extraction unit (12) which extracts a conversion table from the program (P); a table merger unit (13) which generates a merger table by merging the generated-addition table and the extracted conversion table; a random number generation unit (14) which generates a random number; a table randomization unit (15) which generates a randomized merger table by randomizing the merger table using the generated random number; and a converted-program generation unit (16) which generates the converted program (tP) according to the generated randomized merger table.