A locking/assembling structure for a pet bed is disclosed. The locking/assembling structure includes a locating plug, a clamping washer and a bolt. One end of the locating plug is formed with an axially extending projection. Multiple annular fastening plates are fitted around the projection. When the projection is fitted into the opening of each end of a transverse tube of the pet bed, the fastening plates tightly abut against inner wall face of the transverse tube to make the locating plug tightly plugged in the end of the transverse tube. The clamping washer is formed with a central through hole. The outer circumference of the clamping washer is formed with two opposite clamping sections which outward axially obliquely extend. The bolt is passed through a through hole of a longitudinal tube of the pet bed and fitted into the through hole of the clamping washer and screwed into the thread hole of the locating plug. When the bolt is screwed into the thread hole, the clamping sections of the clamping washer gradually converge to tightly clamp the longitudinal tube to make the longitudinal tube and the transverse tube more firmly assembled.
