Threaded Connection for Steel Pipe

A threaded connection for steel pipe is provided that can both provide a certain torque resistance and reduce manufacturing costs. A threaded connection (1) for steel pipe includes a pin (10) including a male thread portion (11) on an outer periphery, and a box (20) including, on an inner periphery, a female thread portion (21) and adapted to be made up on the pin (10). The male thread portion (11) includes a main male thread (111) and an auxiliary male thread (112). The main male thread (111) is constituted by a trapezoidal thread having a constant thread crest width and a constant thread root width. The auxiliary male thread (112) is located on a thread root of the main male thread (111) and has a thread crest width and a thread crest height that are smaller than those of the main male thread (111). In a cross section containing a pipe axis of the pin (10), the flank angle of the stabbing flank (111c) of the main male thread (111) and the flank angle of the loading flank (112d) of the auxiliary male thread (112) at adjacent locations are larger than 0 degrees.