Provided is a fuel supply pump capable of improving welding quality while securing a function of a valve body. A fuel supply pump of the present invention includes a regulating member (discharge valve stopper 84) that guides movement of a valve body (discharge valve 82), a main body portion (body 1) provided with a valve chamber (discharge valve chamber 1d) that houses the regulating member, a sealing member (plug 85) that seals the valve chamber, and a welded portion (welded portion 86) that fixes the sealing member to the main body portion. An annular space portion (annular space portion 60) along an outer periphery of the regulating member is formed between the welded portion and the regulating member. The regulating member includes a positioning portion (fitting portion 84a) for positioning with respect to the main body portion on a side opposite to the sealing member, and a gap forming portion (gap forming portion 84c) forming an annular gap (annular gap 63) between the gap forming portion and the main body portion, and the annular gap allows a space on a side of the positioning portion in the valve chamber and the annular space portion to communicate with each other.