Jonathan Walsh admitted 17 charges of making and distributing indecent images at Exeter Crown Court.
The 47-year-old of Lytham St Annes, Lancashire, was a consultant at North Devon District Hospital.
The Barnstaple hospital sacked him in September 2015 when the police formally charged him. He will be sentenced on 20 March.
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Police found 35 computer files, 34 of which came under category A, meaning they showed the most serious types of abuse.
Det Insp Andrea Kingdon, from Devon and Cornwall Police, said: "He let himself and his profession down by his activities, which he went to great lengths to hide.
"The nature of the offending on the images and videos viewed and distributed by Dr Walsh are at the most serious end of the scale, and some of these included movies some hours in length."
George Thomson, medical director for the Northern Devon Healthcare Trust, said: "This news has deeply shaken our whole team and we know it will also come as a shock to the community."
Police confirmed none of the images related to patients at the hospital.
A paediatrician has pleaded guilty to having and sharing child sex images of the most serious kind.