In this paper, we prove the compressible Euler limit from the Boltzmann equation with hard sphere collisional kernel and complete diffusive boundary condition in half-space by employing the Hilbert expansion which includes interior and Knudsen layers. This rigorously justifies the corresponding formal analysis in Sone’s book [Molecular gas dynamics, Birkhäuser Boston, Inc., Boston, MA, 2007] in the context of short time smooth solutions, and also generalizes the classic Caflisch’s result [Comm. Pure Appl. Math. 33 (1980), pp. 651–666] to initial-boundary problem case.