Abbas al-Sayed was found guilty by a Tel Aviv district court of planning and orchestrating the 2002 Passover suicide bombing at the Park Hotel in Netanya, which killed 30 Israelis.
Sayed was also found guilty of the 2001 bombing at a shopping centre in the seaside city in which five people died.
Sayed, who headed Hamas's military wing in Tulkarm in the occupied West Bank, was convicted of 35 counts of murder and of "being a member of a terrorist organisation", the court said.
The court added that Sayed had the right to appeal the ruling within 45 days.
As he was taken out of court in handcuffs, Sayed told reporters: "The (Israeli) occupation is the most destablising element here. It is the problem."
Hamas, sworn to Israel's destruction, has been behind a campaign of suicide bombings since a Palestinian uprising erupted in 2000 after peace talks failed.
Israel's defence minister, Shaul Mofaz, on Tuesday proposed limited voting in Arab East Jerusalem in this month's Palestinian elections, but the government said it would not tolerate Hamas candidates being on ballots in the city.
Provisional barrier
Meanwhile Mr Mofaz has ordered a "provisional" barrier be built in three areas around east Jerusalem where the high court had ordered construction suspended.
Mr Mofaz insisted that those three sections of the so-called "separation barrier" that Israel is erecting along the length of the West Bank "could be removed when the high court of justice issues its final ruling."
But his decision to press ahead without waiting for the court's decision drew criticism from state television's legal commentator Moshe Negbi.
Mr Negbi accused the defence minister of "trying to create a fait accompli on the ground without any heed for the country's judicial institutions, something tantamount to contempt of court".
Around the holy city's occupied and annexed Arab eastern sector, the barrier takes the form of a tall wall.
About 25 kilometres have been completed and another 40 kilometres are still under construction.
The three sections where the high court ordered work supended last year lie near the Bir Nabala neighbourhood and Shuafat refugee camp to the city's north and the Sheikh Said neighbourhood to its south.
The court decision came in response to an appeal lodged by Palestinian residents, complaining of damage to their livelihoods and quality of life.
Israel has insisted that the barrier is merely designed to prevent attacks on its soil by would-be suicide bombers.