a supporting base including a generally U-shaped first pad and a first magnetic unit having a plurality of first magnetic tablets, said first pad defining a first discharging opening and being formed with a plurality of spaced apart first retaining holes that are distributed along the length of said first pad in such a manner to surround said first discharging opening, each of said first magnetic tablets being received securely in a respective one of said first retaining holes;

a harness unit connected to said supporting base and adapted to harness said supporting base to an animal; and

a collecting device attached magnetically and detachably to said supporting base and including a generally U-shaped second pad, a second magnetic unit having a plurality of second magnetic tablets, and a flexible collecting bag connected to said second pad and defining an inlet, said second pad being formed with a plurality of spaced apart second retaining holes corresponding respectively to said first retaining holes, each of said second magnetic tablets being received securely in a respective one of said second retaining holes and being attracted magnetically to a respective one of said first magnetic tablets so as to permit attachment of said collecting bag to said supporting base and alignment of said inlet of said collecting bag with said first discharging opening of said first pad.