This paper proposes a non-chemical, mechanical giant liposome trapping method using a parylene filter with micrometer-order-sized holes. Giant liposomes can be useful reaction sites for biological assays, where immobilization of the liposomes is the key protocol for microscopic observation. The proposed mechanical trapping method using the parylene filter and gentle flow does not require pretreatments on the liposomes that are time consuming and costly. In addition, this method does not strongly bind but only traps the liposomes, which allows the liposomes to be chemically treated while being trapped and then, to be released. We demonstrated size-dependent trapping, solution exchange and releasing of liposomes. The proposed trapping method and microfluidic device are readily applicable to highly efficient giant liposome assays.