A search for the Standard Model Higgs boson at the Large Hadron Collider (LHC) running at a centre-of-mass energy of 7 TeV is reported, based on a total integrated luminosity of up to 40 pb^-1 collected by the ATLAS detector in 2010. Several Higgs boson decay channels: H -> {\gamma}{\gamma}, H -> ZZ (*) -> llll, H -> ZZ -> ll{\nu}{\nu}, H -> ZZ -> llqq, H -> W W (*) -> l{\nu}l{\nu} and H -> W W -> l{\nu}qq (l is e, {\mu}) are combined in a mass range from 110 GeV to 600 GeV. The highest sensitivity is achieved in the mass range between 160 GeV and 170 GeV, where the expected 95% CL exclusion sensitivity is at Higgs boson production cross sections 2.3 times the Standard Model prediction. Upper limits on the cross section for its production are determined. Models with a fourth generation of heavy leptons and quarks with Standard Model-like couplings to the Higgs boson are also investigated and are excluded for a Higgs boson mass in the range from 140 GeV to 185 GeV. Show Partial Abstract