"My willingness is to help to find an agreement and win the referendum, but my priority today is to understand much more clearly the British requirements in order to avoid any misunderstanding," he said.
Prime Minister David Cameron has promised an in/out referendum by the end of 2017, and is seeking to secure a series of reforms to Britain's membership of the EU before then.
Speaking at the London School of Economics, Macron said he supported Cameron and chancellor George Osborne's ideas about cutting back on red tape and regulation.
But he doesn't have a clear view on what the UK wants to change in the relationship between EU countries, the Eurozone and those outside it.
Separately, Bank of England deputy governor Ben Broadbent told Reuters that the central bank is monitoring the risk that the in/out referendum to Britain's large current account deficit.