In a trenchant editorial in its edition due to appear on Friday, the magazine said it would vote for right-wing incumbent Nicolas Sarkozy in the May 6 run-off if it had the opportunity.
"We would give it to Mr Sarkozy but not on his merits, so much as to keep out Mr Hollande," it said.
The editorial underscored that France desperately needed reform.
"Public debt is high and rising, the government has not run a surplus in over 35 years, the banks are undercapitalised, unemployment is persistent and corrosive and, at 56% of GDP, the French state is the biggest of any euro country," it said.
Hollande's "programme seems a very poor answer to all this especially given that France's neighbours have been undergoing genuine reforms," it said, stressing that he "talks a lot about social justice, but barely at all about the need to create wealth.
"Although he pledges to cut the budget deficit, he plans to do so by raising taxes, not cutting spending.
"Mr Hollande has promised to hire 60,000 new teachers. By his own calculations, his proposals would splurge an extra 20 billion (euros) over five years. The state would grow even bigger."
The editorial however said that with a Socialist president "France would get one big thing right. Mr Hollande opposes the harsh German-enforced fiscal tightening which is strangling the eurozone's chances of recovery".
"But he is doing this for the wrong reasons and he looks likely to get so much else wrong that the prosperity of France (and the eurozone) would be at risk."
"Mr Hollande evinces a deep anti-business attitude. He will also be hamstrung by his own unreformed Socialist Party and steered by an electorate that has not yet heard the case for reform, least of all from him," it added.
The Economist said Hollande was opposed to reform simply "to preserve the French social model at all costs", adding it was "no wonder" that German Chancellor Angela Merkel said she would campaign against him.
"Every German chancellor eventually learns to tame the president next door, and Mr Hollande would be a less mercurial partner than Mr Sarkozy," it said.
"But his refusal to countenance structural reform of any sort would surely make it harder for him to persuade Mrs Merkel to tolerate more inflation or consider some form of debt mutualisation.
"Mr Hollande is not suggesting slower fiscal adjustment to smooth the path of reform: he is proposing not to reform at all." Summing up, the weekly said: "A French president so hostile to change would undermine Europe's willingness to pursue the painful reforms it must eventually embrace for the euro to survive. That makes him a rather dangerous man."