The present invention provides a silencer having improved ease of maintenance and a small size and light weight and a respiratory assistance device. The silencer is provided to therapy equipment where pressurized air is generated by a blower, and the pressurized air is supplied to an airway of a patient from an attachment part attached to the patient, the silencer being inserted into a flow passage so as to reduce sound generated by the therapy equipment, the pressurized air being introduced from the blower to the patient through the flow passage, wherein the silencer is provided outside a casing which accommodates the blower.
