1. A non-transitory, computer-readable recording medium storing a physical quantity distribution calculation program to be executed by a computer that causes a display to visualize a physical quantity distribution in a target space for numerical analysis, the program causing the computer to perform the processes of: based on positional information on a plurality of grid points defined in the target space and physical quantities obtained respectively at the plurality of grid points by the numerical analysis, grouping the plurality of grid points into groups of neighboring grid points having the same physical quantity; and determining the physical quantity to be visualized by each of a plurality of pixels of the visualization device which are used to visualize and display the physical quantities obtained respectively at the plurality of grid points by the numerical analysis and are fewer than the plurality of grid points, the determining process including extracting for the respective pixels, from the groups formed in the grouping process, at least one group including at least one of grid points corresponding to the pixel out of the plurality of grid points, identifying the group including the largest number of grid points among the extracted groups, and determining that the physical quantity at the grid points belonging to the identified group is the physical quantity to be visualized by the pixel.