Quantum computing technology has been developing rapidly in recent years, and it is expected to speed up some kinds of computation that are highly time-consuming in classical computing, e.g., operations on extremely large matrices. Practical applications in various fields are being explored, and cosmology is one of them. In this talk, after an introduction to quantum computing, I explain its application in stochastic inflation, a formalism for analyzing the inflationary perturbation based on the probability theory. In this formalism, the perturbation is related to the Fokker-Planck equation, and its probability distribution is characterized by the eigenvalues of the differential operator. However, calculating them can be challenging, especially in multi-field cases, since it corresponds to finding eigenvalues of an exponentially large matrix. I explain a quantum algorithm to calculate the differential operator eigenvalues efficiently and share results from numerical demonstrations that suggest its applicability to the stochastic inflation problem.