Secondary cutaneous amyloidosis refers to clinically unapparent amyloid deposits within the skin in association with a pre-existing skin condition or skin tumors, such as basal cell carcinoma, porokeratosis, solar elastosis, Bowen's disease, and mycosis fungoides. A 70-year-old woman presented with a 6-month history of asymptomatic multiple yellowish plaques on both legs. She had been diagnosed with mycosis fungoides 7 years ago and was treated with psoralen and ultraviolet A radiation (PUVA) therapy, narrow-band ultraviolet B (UVB) therapy, and acitretin for 5 years. Finally, she reached complete remission of mycosis fungoides. However, new yellowish lesions started to appear 1 year after discontinuing the phototherapy. A physical examination revealed multiple yellowish plaques on both extremities. The plaques were well circumscribed and slightly elevated. All laboratory tests were normal. A biopsy specimen showed multiple nodular deposits of eosinophilic amorphous material in papillary dermis and upper reticular dermis. The deposits represented apple green birefringence on Congo red stain viewed under polarized light. Acellular small nodules in the upper dermis consisted of randomly oriented, non-branching, 6.67~12.7 nm thick amyloid fibrils on electron microscopy. We report an interesting and rare case of secondary cutaneous amyloidosis after narrow-band UVB therapy and PUVA therapy in a patient with mycosis fungoides.