Inclusive, differential and production mode cross sections of the Higgs boson production in proton-proton collisions are measured in the decay channel. The protonproton collision data were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector from 2015 to 2017, corresponding to an integrated luminosity of 79.8 fb. The inclusive fiducial cross section for the process is measured to be fb, while the Standard Model prediction is fb. The cross-section times branching ratio for gluon fusion and vector-boson fusion production are measured to be pb and pb, respectively. All measurements are in agreement with the Standard Model prediction.