Jane Couch, 29, known as the Fleetwood Assassin after her home town in Lancashire, complained to an industrial tribunal last month that she was being discriminated against as she could not compete in the UK at men's fights without a licence.
The tribunal, in Croydon, south London, heard that Miss Couch could expect to earn between £10,000 and £20,000 every two months if she had been licensed.
She Couch could now seek damages for loss of earnings and hurt feelings.
The board contended at the tribunal that women should not be licensed to box because pre-menstrual tension made them unstable.
Miss Couch told the hearing she had to turn down a £10,000 fight at the Wembley Arena last year because she did not have a licence.
She was supported by the Equal Opportunities Commission which said she was being denied the opportunity to box professionally because of her sex.
The commission said last month that if the case was won, the traditionally male preserve of professional boxing would be open to all suitably qualified women.
Ms Couch will have to re-apply to the board for a licence but this could take some time and it could turn her down again.
The board had no immediate comment on the decision.
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