A heat gun having improved flow effects, includes a head portion, comprising: the head portion defining a flow passage, wherein the flow passage extends longitudinally along an axis, has an inlet end at one end and an outlet end at another opposite end, and includes an inlet portion, an outlet portion and a flow guiding portion disposed between the inlet and outlet ends (211, 212), wherein the outlet portion is formed with two long sides and two short sides, with the two long sides opposite one another, and with the two short sides opposite one another, wherein the flow guiding portion is disposed between the inlet and outlet portions (213, 214), characterized in that the flow passage includes two flow guiding protrusions disposed at the flow guiding portion, wherein the two flow guiding protrusions are disposed oppositely, wherein the two flow guiding protrusions extend oppositely along the long sides, wherein the flow guiding portion is partitioned by the two flow guiding protrusions and defines a first flow region which extends along a first extension axis, a second flow region which extends along a second extension axis and a third flow region, wherein the third flow region is disposed between the two flow guiding protrusions, wherein the third flow region includes a side connected to the first flow region and an opposite side connected to the second flow region, wherein the first flow region extends from a first end which is adjacent to the inlet portion to a second end which is adjacent to the outlet portion and has a gradually reduced cross-section from the first end to the second end, wherein the first flow region has a middle portion which is in the middle between the inlet portion and the outlet portion and which has a radial cross-section about the first extension axis greater than 0.25 times and smaller than 0.4 times of a radial cross-section of the inlet portion about the axis, wherein the second flow region extends from a first end which is adjacent to the inlet portion to a second end which is adjacent to the outlet portion and has a gradually reduced cross-section from the first end to the second end, wherein the second flow region has a middle portion which is in the middle between the inlet portion and the outlet portion and which has a radial cross-section about the second extension axis greater than 0.25 times and smaller than 0.4 times of the radial cross-section of the inlet portion. the head portion defining a flow passage, wherein the flow passage extends longitudinally along an axis, has an inlet end at one end and an outlet end at another opposite end, and includes an inlet portion, an outlet portion and a flow guiding portion disposed between the inlet and outlet ends (211, 212), wherein the outlet portion is formed with two long sides and two short sides, with the two long sides opposite one another, and with the two short sides opposite one another, wherein the flow guiding portion is disposed between the inlet and outlet portions (213, 214), characterized in that the flow passage includes two flow guiding protrusions disposed at the flow guiding portion, wherein the two flow guiding protrusions are disposed oppositely, wherein the two flow guiding protrusions extend oppositely along the long sides, wherein the flow guiding portion is partitioned by the two flow guiding protrusions and defines a first flow region which extends along a first extension axis, a second flow region which extends along a second extension axis and a third flow region, wherein the third flow region is disposed between the two flow guiding protrusions, wherein the third flow region includes a side connected to the first flow region and an opposite side connected to the second flow region, wherein the first flow region extends from a first end which is adjacent to the inlet portion to a second end which is adjacent to the outlet portion and has a gradually reduced cross-section from the first end to the second end, wherein the first flow region has a middle portion which is in the middle between the inlet portion and the outlet portion and which has a radial cross-section about the first extension axis greater than 0.25 times and smaller than 0.4 times of a radial cross-section of the inlet portion about the axis, wherein the second flow region extends from a first end which is adjacent to the inlet portion to a second end which is adjacent to the outlet portion and has a gradually reduced cross-section from the first end to the second end, wherein the second flow region has a middle portion which is in the middle between the inlet portion and the outlet portion and which has a radial cross-section about the second extension axis greater than 0.25 times and smaller than 0.4 times of the radial cross-section of the inlet portion.