Dumbell adjustable in weight

A dumbbell comprising:

• a carrying seat formed of two plates parallel to each other, two hollow rods, and a grip;
• each of said plates provided with at least one through hole corresponding in location to one of said hollow rods, and a plurality of carrying grooves, one of said plates provided with a receiving cell;
• a plurality of weights with each of said weights formed of a pair of block bodies identical to each other and having a plurality of through holes corresponding in location to said through holes of said plates, and a plurality of carrying grooves;
• each said pair of block bodies provided with two connection rods disposed therebetween, said connection rods being different in length between different pairs of block bodies so as to enable said weights to be juxtaposed on said carrying seat, and to enable each said connection rod to press against respectively one of said carrying grooves;
• and
• a selection device disposed in said receiving cell and composed of an adjustor, at least one cord, at least one steering mechanism, and at least two pins disposed in said hollow rods such that each said pin is connected at one end thereof with the adjustor, and the other end of said pins correspond to said through holes of said plates, and that said pins are simultaneously extracted from or retracted into said hollow rods when said adjustor is adjusted in position thereof, thereby resulting in said pins extending into said through holes of said block bodies of selected said weights.