LiteBIRD is a space-borne experiment dedicated to detecting large-scale B-mode anisotropies of the linear polarization of the cosmic microwave background (CMB) predicted by the theory of inflation. It is planned to be launched in the late 2020s to the second Lagrangean point of the Sun-Earth system and map the sky in 15 frequency bands using thousands of transition edge sensor bolometers. LiteBIRD will be exposed to the cosmic-ray radiation throughout its lifetime, which may lead to the degradation of the scientific performance. Energy deposition by cosmic rays upon the focal plane bolometer detectors is considered a serious source of systematic effects. For a quantitative assessment of the effect, we present the result of Geant4 simulations to estimate the energy deposited by cosmic rays into the focal plane. We simulated different cosmic-ray components using CAD-based spacecraft models. We derive the spatial and energy distribution of the particles in the focal plane.