The survey came as the prosecution was to present its closing arguments to the Oslo district court on Thursday.
When asked the question "Is Breivik of sufficiently sound mind to be convicted?", 74 percent of respondents replied "yes", while 10 percent said he could not be held responsible for his actions and needed "medical treatment."
Fifteen percent said they were undecided or refused to answer.
At the end of its closing arguments on Thursday, the prosecution will reveal whether it wants Breivik to be sent to prison or a closed psychiatric ward.
They will base their request on psychiatric evaluations of the 33-year-old right-wing extremist which have sharply contradicted each other.
In the formal indictment presented in March, in which Breivik was charged with "acts of terror", the two prosecutors called for him to be committed to psychiatric care but left the door open to change their minds if new information were to surface about his mental health.
Breivik has confessed to the killings but pleaded not guilty, saying his actions were "cruel but necessary" to save Norway from a wave of multiculturalism and a "Muslim invasion".
The trial, which opened on April 16th and is due to conclude on Friday when the defence presents its closing arguments, has focused largely on whether or not Breivik is criminally sane.
While the psychiatric evaluations of Breivik have come to starkly opposing conclusions, most of the psychiatrists and psychologists who have observed him and who testified during the trial said they believed him to be sane.
Thursday's poll, conducted by public broadcaster NRK, questioned 1,000 Norwegians last week as a slew of psychiatrists were testifying in court.
On July 22nd, Breivik first set off a car bomb outside government buildings in Oslo, killing eight people, before travelling to Utøya island, north-west of the capital, where he spent more than an hour methodically shooting and killing another 69 people, mostly teenagers.
Breivik wants to be found sane so that his Islamophobic ideology is not written off as the ravings of a lunatic, even if it means a long prison sentence.
The verdict is expected on either July 20th or August 24th.