Abstract: A fluid analyzer including a physical property value setting section 2 for setting a physical property value in accordance with grid information for boundary conditions and object positions, a number-of-dimension control section 5 for controlling the number of dimensions of a space to be analyzed, a momentum correction section 51 for automatically correcting the momentum of the speed vector of an inlet or outlet, and a boundary condition control section 4 for automatically setting a boundary condition not diverged even in natural convection computation, which repeats repetitive computation until resulting in convergence after generating grids. Thereby, it is possible to accurately set a physical property value and an analysis dimension according to grid division, correct a momentum, and control natural convection computation.