PURPOSE: This invention is to provide a gap for a light distribution control member to be disposed, between the lower end periphery of each equipment main body and each ceiling bar only with upward force applied to each equipment main body.

CONSTITUTION: Plural rectangular holding holes 36 are provided for each mounting frame 3 fixed onto ceiling bars 1. Each equipment main body 2 is provided with each engaging projected piece 26 which is formed out of an elastic metallic plate so as to be engaged with each holding hole 36. The upper piece 26a of each engaging projected piece 26 is slanted downward as it is projected. When the lower piece 26b of each engaging projected piece 26 is rested on the lower end periphery of each holding hole 36, each equipment main body 1 is prohibited from being moved downward. When upward force is applied to each equipment main body 2, each engaging projected piece 26 is pushed in each equipment main body 2 with the upper piece 26a of each engaging projected piece 26 pushed to the upper end periphery of each holding hole 36, each equipment main body 2 is thereby moved upward.