Abstract: A filter that can make a reflection delay of an initial stage coupling part correspond to a change in a passband due to a manufacturing error of a substrate or the like is realized. A filter according to an example embodiment includes: a substrate having a dielectric property; an initial stage coupling part formed on the substrate; and an interstage coupling part formed on the substrate. The initial stage coupling part is formed so that a reflection delay is decreased in accordance with an increase in a passband due to a manufacturing error of the substrate or the interstage coupling part, or so that the reflection delay is increased in accordance with a decrease in the passband.