It is an objective of the invention to provide a quasi-solid state electrolyte that has a well-balanced combination of contact performance with electrode active materials, conductivity, and chemical and structural stability, each at a high level, and an all solid state lithium secondary battery using the quasi-solid state electrolyte. There is provided a quasi-solid state electrolyte comprising: metal oxide particles; and an ionic conductor, the ionic conductor being a mixture of either a glyme or DEME-TFSI and a lithium salt that includes LiFSI, and being carried by the metal oxide particles.