The attack on the guard, who worked for Brink's, happened in Colombes, a suburb to the north-west of Paris.
His attackers grabbed him outside his home and forced him to put on the belt, telling him it was linked to a mobile phone.
They told him that he had to get €600,000 and bring it back to them or they would detonate the explosives.
The brave guard kept his cool and called the police. They sent in a team of experts to defuse the explosives, which turned out to be fake.
The same approach was used in an earlier attack in mid-July in the same part of Paris. On that occasion the attackers successfully demanded a sum of €250,000.
Two suspects aged 19 and 23 were arrested on Monday in connection with the attack.