Eaton's closure proposals are the latest to hit Anglesey's economy
Eaton's decision is the latest in a series of manufacturing job losses on the island in recent years.
In 2004, a 100 jobs were lost with the closure of the Hedstrom toy factory in Holyhead.
Prior to that, the Great Lakes bromine plant shut its operation at Amlwch with the loss of another 100 posts.
In April this year, Eastman Chemicals said it was closing it Peboc site at Llangefni, ending 40 years association with the town, at the cost of 65 staff.
There is also an uncertain future for the islands two biggest employers - Anglesey Aluminium and Wylfa nuclear power station.
The power station is set to halt generation in 2010, when decommissioning of the ageing reactor begins. It also supplies the bulk of the electricity needed to run the power-hungry operations at the aluminium site.
Between them, the two operations employ around 1,500 people.
Dewi Lloyd, the manager of Holyhead Regeneration, said Eaton's announcement would be challenging for both the town and the island.
"It's going to be a major blow," he said. "A lot of the people working there live near the factory - they are going to find it very difficult.
"It's definitely true that we've seen a decline in particularly manufacturing on the island over the years, while we have seen gains in the service and retail sector.
"However, many of those retail jobs are part-time - not the full-time skilled manufacturing posts we have at somewhere like Eaton."
Mr Lloyd also pointed to positive developments on the island, including the imminent opening of a Morrisons supermarket, bringing 350 jobs.
RAF Valley is expanding its role as the UK's fast jet training centre and Mr Lloyd said he hoped work could be found in civilian developments there for some of the Eaton workforce.
However, recent economic figures for Anglesey show it faces an uphill battle on the jobs front.
In August, the number of people claiming job seeker's allowance on the island stood at nearly 1,200, which at 3% of the working age population remains higher than averages for Wales or England.