A headphone type acoustic apparatus, comprising: a headband having two end portions; a pair of slider blocks (20R, 20L), wherein each slider block (20R, 20L) of the pair of slider blocks (20R, 20L) slidably retains a respective end portion of the headband; a pair of housing blocks (40R, 40L), wherein each housing block (40R, 40L) of the pair of housing blocks (40R, 40L) is coupled to a corresponding slider block of the pair of slider blocks (20R, 20L) via coupling portions, and wherein each housing block (40R, 40L) of the pair of housing blocks (40R, 40L) includes a headphone unit; and a pair of speaker units, wherein each speaker unit of the pair of speaker units is disposed in each slider block of the pair of slider blocks (20R, 20L), wherein each of the pair of speaker units is arranged to transmit sound to a user by vibrating air in a surrounding open space, and wherein each headphone unit is arranged to transmit sound to the user by vibrating air in a space closed by the housing blocks (40R, 40L), characterized in that, each of the pair of the speaker units further comprising: a speaker driver unit including a diaphragm that is configured to convert electrical signals into vibration of air in a direction of inside to outside of each corresponding slider block (20R, 20L); a magnetic circuit that is configured to drive the diaphragm; a case (242, 243) that retains and houses the diaphragm and the magnetic circuit; and a lid (244, 245) that includes an opening for spilling sound in a direction orthogonal to a slide direction of each corresponding slider block (20R, 20L), wherein the opening is on a front side in a state in which the headphone type acoustic apparatus is worn by the user. a headband having two end portions; a pair of slider blocks (20R, 20L), wherein each slider block (20R, 20L) of the pair of slider blocks (20R, 20L) slidably retains a respective end portion of the headband; a pair of housing blocks (40R, 40L), wherein each housing block (40R, 40L) of the pair of housing blocks (40R, 40L) is coupled to a corresponding slider block of the pair of slider blocks (20R, 20L) via coupling portions, and wherein each housing block (40R, 40L) of the pair of housing blocks (40R, 40L) includes a headphone unit; and a pair of speaker units, wherein each speaker unit of the pair of speaker units is disposed in each slider block of the pair of slider blocks (20R, 20L), wherein each of the pair of speaker units is arranged to transmit sound to a user by vibrating air in a surrounding open space, and wherein each headphone unit is arranged to transmit sound to the user by vibrating air in a space closed by the housing blocks (40R, 40L), characterized in that, each of the pair of the speaker units further comprising: a speaker driver unit including a diaphragm that is configured to convert electrical signals into vibration of air in a direction of inside to outside of each corresponding slider block (20R, 20L); a magnetic circuit that is configured to drive the diaphragm; a case (242, 243) that retains and houses the diaphragm and the magnetic circuit; and a lid (244, 245) that includes an opening for spilling sound in a direction orthogonal to a slide direction of each corresponding slider block (20R, 20L), wherein the opening is on a front side in a state in which the headphone type acoustic apparatus is worn by the user. a speaker driver unit including a diaphragm that is configured to convert electrical signals into vibration of air in a direction of inside to outside of each corresponding slider block (20R, 20L); a magnetic circuit that is configured to drive the diaphragm; a case (242, 243) that retains and houses the diaphragm and the magnetic circuit; and a lid (244, 245) that includes an opening for spilling sound in a direction orthogonal to a slide direction of each corresponding slider block (20R, 20L), wherein the opening is on a front side in a state in which the headphone type acoustic apparatus is worn by the user.