A design assistance method executed by a design assistance device for a computer system including a CPU and an accelerator, the design assistance method includes: extracting, from an input program described in a high-level language, a process including a function and data including a variable, and analyzing a relationship between a process and data, the relationship including an amount of access from the process to the data, based on a number of times of execution of the function or a loop; evaluating, for the acquired process, a used amount of resource, a delay, and a communication band of the accelerator, based on a hardware specification; and generating, for the acquired process and data, candidates represented by a combination of allocations to the CPU and the accelerator, and acquiring and presenting, for each of the candidates, a used amount of resource, a communication band, and performance of the input program.