To provide a filter such as an air filter to be installed in a pipe and whose maintenance can easily and simply be carried out.

Since a member 30 for temporary engagement which can temporarily engage an upper housing 3 and a lower housing 4 to be divided at the time of exchanging filter elements 11 is installed, a work of attaching and detaching the lower part housing 4 to and from the upper part housing 3 can be carried out even in the state that an installation band 18 is taken out and a work of fixing these housings by the installation band 18 can be carried out separately from the former work. Consequently, a separating or assembling work can easily and reliably be carried out even by one worker and a filter 10 with excellent work efficiency is obtained.