The present invention aims to provide a windowed envelope in which the sender's name is printed on the contents enclosed, such as a delivery slip, and the recipient of the envelope can visually identify the sender's address, name, etc., without having to print them on the back of the envelope, as long as the contents are enclosed. [Solution] The present invention comprises an envelope body formed in a rectangular shape, with three sides of the rectangle closed and one side open for inserting an item, a translucent address window provided at a predetermined position on the front surface of the envelope body and sized to be sufficient for displaying the recipient's address, and a translucent sender window provided at a predetermined position on the back surface of the envelope body and sized to be sufficient for displaying the sender's address.