The death brings to 11 the number of Gazans killed in four separate collapses since January 26, and comes with Israeli concern building over the reconstruction of tunnels it says could be used for attacks.
Israel's military chief of staff Gadi Eisenkot said day that militant tunnels in Gaza were now the army's main priority.
The Ezzedine Al-Qassam Brigades, Hamas's military wing, said in a statement that Marwan Maarouf, 27, from Khan Yunis in the southern Gaza Strip, died "after the collapse of a resistance tunnel".
Ten other Palestinians have died in three tunnel collapses in the past two weeks, nine of them members of the Ezzedine Al-Qassam Brigades.
During previous conflicts with Israel, Hamas forces have used the tunnels to avoid or carry out attacks, store weapons and at times to enter Israel. Hamas says it needs the tunnels to defend itself against Israeli firepower.
Palestinian militants in Gaza have fought three wars with Israel since 2008.
Gazans have also used tunnels along the Egyptian border for smuggling.
In late 2014, Egypt began setting up a buffer zone on its border with Gaza, and destroyed hundreds of tunnels it says are used for smuggling weapons and other items.
In September 2015, Egyptian forces carried out digging work that Palestinians say led to the flooding of the last remaining tunnels there.
On Saturday Israeli Energy Minister Yuval Steinitz said the tunnels were flooded by Egypt at Israel's request. His office later said the remarks were misinterpreted.
