Radiation-induced skin ulcer following cancer and/or tumour is well-documented in the literature. However, radiation-induced skin ulcer following the excision of keloid is yet to be reported. Here, we report the case of a 33-year-old female patient with a suprapubic skin ulcer of five months' duration following keloid treatment with electron beam therapy at recommended dosage. Various examinations, including a skin biopsy, metagenomic sequencing, magnetic resonance imaging and immunochemistry, indicated that the skin ulcer was induced by radiotherapy. While postoperative radiotherapy has been recommended immediately following keloid excision to reduce the risk of recurrence, the present case highlights the risk of skin refractory ulcer following keloid radiotherapy.