An acoustic wave device includes: a substrate; a functional element that is located on the substrate and excites acoustic waves; a side wall portion that is made of a metal and is located on the substrate so as to surround the functional element; a metal plate that is located above the functional element and the side wall portion, and seals the functional element so that a space is formed above the functional element; and a terminal that is located on the substrate and further out than the side wall portion, and is electrically connected to the functional element.