A filter head having a filter head main body comprising: an inflow passage communicating with an inflow portion; an outflow passage communicating with an outflow portion; a filter introduction hole communicating with the inflow passage, to which an introduction portion of a filter is connected when the filter is mounted to allow a partial flow of a fluid introduced through the inflow portion to be introduced to the filter; a filter discharge hole communicating with the outflow passage, to which a discharge portion of the filter is connected when the filter is mounted to allow a fluid which has passed through the filter to be expelled through the outflow portion; first and second opening and closing units (140, 150) provided in the filter head main body such that, when the filter is mounted, the first and second opening and closing units (140, 150) allow the inflow passage and the filter introduction hole, and the outflow passage and the filter discharge hole, to communicate with each other, respectively, and when the filter is separated, the first and second opening and closing units (140, 150) do not allow the inflow passage and the filter introduction hole, and the outflow passage and the filter discharge hole, to communicate with each other, respectively characterized in that: a bypass flow channel connects the inflow passage and the outflow passage and allows the remaining flow of the fluid introduced through the inflow portion to pass therethrough so as to be expelled together with the fluid which has passed through the filter, through the outflow portion; and wherein the first and second opening and closing units (140, 150) are configured to allow a partial flow of the fluid introduced through the inflow portion to pass through the bypass flow channel when the filter is mounted, and a gap is formed between the filter head main body and the first and second opening and closing units (140, 150) when the filter is mounted in order to allow a partial flow of the fluid introduced through the inflow portion to pass through the bypass flow channel, one or more of the first and second opening and closing units (140, 150) include a gap adjusting unit for adjusting the gap, and the gap adjusting unit includes a manipulation portion protruded to the outside of the filter head main body and a variable portion changing a width of the gap according to an operation of the manipulation portion. an inflow passage communicating with an inflow portion; an outflow passage communicating with an outflow portion; a filter introduction hole communicating with the inflow passage, to which an introduction portion of a filter is connected when the filter is mounted to allow a partial flow of a fluid introduced through the inflow portion to be introduced to the filter; a filter discharge hole communicating with the outflow passage, to which a discharge portion of the filter is connected when the filter is mounted to allow a fluid which has passed through the filter to be expelled through the outflow portion; first and second opening and closing units (140, 150) provided in the filter head main body such that, when the filter is mounted, the first and second opening and closing units (140, 150) allow the inflow passage and the filter introduction hole, and the outflow passage and the filter discharge hole, to communicate with each other, respectively, and when the filter is separated, the first and second opening and closing units (140, 150) do not allow the inflow passage and the filter introduction hole, and the outflow passage and the filter discharge hole, to communicate with each other, respectively a bypass flow channel connects the inflow passage and the outflow passage and allows the remaining flow of the fluid introduced through the inflow portion to pass therethrough so as to be expelled together with the fluid which has passed through the filter, through the outflow portion; and wherein the first and second opening and closing units (140, 150) are configured to allow a partial flow of the fluid introduced through the inflow portion to pass through the bypass flow channel when the filter is mounted, and a gap is formed between the filter head main body and the first and second opening and closing units (140, 150) when the filter is mounted in order to allow a partial flow of the fluid introduced through the inflow portion to pass through the bypass flow channel, one or more of the first and second opening and closing units (140, 150) include a gap adjusting unit for adjusting the gap, and the gap adjusting unit includes a manipulation portion protruded to the outside of the filter head main body and a variable portion changing a width of the gap according to an operation of the manipulation portion.