A hand grenade simulating device includes a first shell filled with a marking filler, a second shell disposed in the first shell for receiving a percussion-triggered charge, a striking member which is remote from the charge in a ready position and which is movable to strike the charge by a biasing force of a biasing member to initiate detonation for exploding the first and second shells and scattering the marking filler, a releasably retaining member which is disposed to hold the striking member in the ready position and which is manually releasable, and a delay member disposed to generate a kinetic frictional force between the striking member and the second shell such that the striking member is dragged by the frictional force against the biasing force of the biasing member when the releasably retained member is released.