The invention discloses a support device for a reciprocating saw, and belongs to the field of electric tools. The problem that the support device for the reciprocating saw is inconvenient to adjust is solved. According to the technical scheme, the support device mainly comprises a tooth box with a sliding groove and a support plate, the support plate is connected into the sliding groove in a sliding manner, and positioning holes arranged in the sliding direction of the support plate are formed in the supporting plate; a locking pin is arranged on the tooth box and comprises a locking part matched with the positioning holes to achieve locking and an adjusting part connected with the locking part, and the adjusting part is movably connected to the tooth box; and the support plate is provided with an adjusting channel communicated with the adjacent positioning holes, and in the transverse direction perpendicular to the sliding direction of the support plate, the width of the adjusting channel is smaller than the transverse direction size of the locking part and larger than the transverse direction size of the adjusting part. According to the support device, adjustment is rapid and convenient, and the structure is simple.