This compares to 361,202 people at the end of April 2019, meaning an annual rise of 58 percent.
The AMS called the spike since mid-March this year "an extreme rise in inactivity linked to coronavirus".
The unemployment rate, which in Austria is calculated to include those in training, stood at 12.8 percent at the end of April, up from 8.1 per cent in February.
AMS said in a statement that "all sectors, all regions and all age groups" had been affected by the slowdown.
There are now ten times more jobseekers than vacancies, which are themselves down a third year-on-year.
The hardest hit industries are hotels and restaurants, which have seen a 130 per cent rise in unemployment, and construction, where the figure is 98 per cent.
The mountainous Tyrol region, where the vital ski season had to be ended early, saw a 108 per cent spike.
Austria moved into a lockdown to restrict the virus's spread relatively early in mid-March, and is now in the process of progressively lifting restrictions on movement.
As of Monday the country of 8.8 million people had recorded 15,538 infections and 600 deaths.