Just like all other dogs you only need to bathe the French Bulldog every few weeks to once per month.
That is unless the French Bulldog gets muddy or dirty and needs a bath more often than that.
If you need to bathe the French Bulldog to get it clean then do so.
But other than that a French Bulldog only needs a bath only once per month or every few weeks.
Bathing a French Bulldog or any other dog more often than needed can strip the dogs skin of essential natural oils that keep it's hair shiny.
When you bathe the dog too often those oils get stripped out which can lead to the hair drying out as well as the skin drying out and then the hair could fall out more as well.