A parallel computer system including a plurality of processors configured to perform LU factorization in parallel, the system is configured to cause each of the plurality of processors to execute processing including: generating a first panel by integrating a plurality of row panels among panels of a matrix to be subjected to the LU-factorization, the plurality of row panels being processed by the processor, generating a second panel by integrating a plurality of column panels among the panels of the matrix, the plurality of column panels being processed by the processor, and computing a matrix product of the first panel and the second panel. In parallel with the computation of the matrix product, each processor is configured to receive or transmit a column panel to be used for computation of a subsequent matrix product from or to another processor among the plurality of processors.