A package for high frequency waves containing therein a high frequency electronic circuit, the package comprising: an hermetic box-shaped high frequency package (11, 12, 13) containing the high frequency electronic circuit in the inside and shielded by a conductor; and an input terminal and an output terminal partly led out to the outside of the high frequency package; and an input side feed-through section having one of its opposite ends connected to the input terminal and the other end connected to the high frequency electronic circuit and having a predetermined characteristic impedance; and an output side feed-through section having one of its opposite ends connected to the output terminal and the other end connected to the high frequency electronic circuit and having a characteristic impedance lower than the characteristic impedance of the input side feed-through section as viewed from the output terminal side, and wherein each of the input side feed-through section and the output side feed-through section has a first micro-strip line (32; 37) connected to the high frequency circuit, a second micro-strip line (30; 39) connected to the respective terminal (10; 15) and having a predetermined line width, and a respective feed-through line (31; 38) connecting the first and second micro-strip lines (30, 32; 37, 39), at least the line width of the feed-through line of the output side feed-through section is greater than the line width of the feed-through line of the input side feed-through section, while the width of the output terminal is greater than the width of the input terminal, and each feed-through line (31, 38) has a width less than the first and second micro-strip lines (30, 32; 37, 39) it connects. an hermetic box-shaped high frequency package (11, 12, 13) containing the high frequency electronic circuit in the inside and shielded by a conductor; and an input terminal and an output terminal partly led out to the outside of the high frequency package; and an input side feed-through section having one of its opposite ends connected to the input terminal and the other end connected to the high frequency electronic circuit and having a predetermined characteristic impedance; and an output side feed-through section having one of its opposite ends connected to the output terminal and the other end connected to the high frequency electronic circuit and having a characteristic impedance lower than the characteristic impedance of the input side feed-through section as viewed from the output terminal side, and wherein each of the input side feed-through section and the output side feed-through section has a first micro-strip line (32; 37) connected to the high frequency circuit, a second micro-strip line (30; 39) connected to the respective terminal (10; 15) and having a predetermined line width, and a respective feed-through line (31; 38) connecting the first and second micro-strip lines (30, 32; 37, 39), at least the line width of the feed-through line of the output side feed-through section is greater than the line width of the feed-through line of the input side feed-through section, while the width of the output terminal is greater than the width of the input terminal, and each feed-through line (31, 38) has a width less than the first and second micro-strip lines (30, 32; 37, 39) it connects.