The Japan-based company, best known for its electronics, is a "serious and long-term investor in the UK", Nakanishi continued, as he explained how Brexit will affect Hitachi.
"We have invested over £1bn creating new jobs in the UK’s rail and energy sectors," he added.
"Together Japanese investors provide 140,000 direct jobs in the UK, and many more in the supply chain."
But, writing in The Mirror, he said the critical benefit for investing in the UK was that it is "the best base for accessing the whole European market of 500m people".
Nakanishi's comments echo arguments made by Remain campaigners, who have stressed access to the single market as a key benefit of EU membership.
"There are other reasons like the size of the UK market, availability of local and international talent and the support of our local communities – which is why we take a positive view of the UK inside Europe," he wrote.
"Therefore we have our regional headquarters here and moved our global rail headquarters to London.
"But take away the UK’s membership of the EU, and the future investment case looks very different."
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He echoed the Remain campaign again by pointing out those advocating Brexit "have no answer to how the UK could negotiate cost-free access to this huge market from a position outside it".
Leave campaigners have come under pressure to explain how they could strike a uniquely British deal with he EU, based on free trade, while taking back control of the UK's borders and stopping EU immigration.
Negotiating "would take a long time and result in uncertain market conditions; during this renegotiation period, investors would probably be waiting to see the outcomes, hold back on investment, and jobs would be lost," Nakanishi added.