A language conversion method includes a first process in which a computer unit inputs algorithm description data describing an algorithm of hardware under a predetermined description constraint using a program description language, a second process in which the computer unit inputs hardware element specification data specifying parameters representing hardware elements included in the algorithm description data, and a third process in which the computer unit converts the algorithm description data into data of a hardware model based on a system level description language, wherein, in the third process, the computer unit generates a data dependency preservation description which preserves, in the hardware model, data dependency in the algorithm description with regard to a parameter specified in the hardware element specification data.